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genetics exam 2 (SI notes)

front 1

What are the 2 forms of dominance?

back 1

Incomplete and codominance

front 2

What is incomplete dominance?

back 2

occurs when there is not a distinct dominant allele shown in the heterozygote. ex: a mix of a red and white flower making it pink

front 3

What is codominance?

back 3

occurs when BOTH the dominant and recessive alleles are detectable in the heterozygous organism. ex: a brown and white cow makes a brown cow with white spots

front 4

What are lethal alleles?

back 4

A gene is so mutated, that if an organism has two mutated copies, it will not survive to term

front 5

What is a recessive lethal allele?

back 5

lethal alleles are naturally selected out of the population, as there is no
viable phenotype

front 6

What are dominant lethal alleles?

back 6

lethal alleles still exist at low levels. This is because heterozygotes still carry the lethal alleles

front 7

What can lethal alleles cause?

back 7

They can kill an offspring before it reaches term, or they can have a delayed age of onset

front 8

What is happlosufficency?

back 8

means that with only one Wild type allele, you produce the normal
phenotype (typically dominant)

front 9

What is happloinsufficency?

back 9

means that only one Wild type allele can NOT produce the normal
phenotype (typically dominant)

front 10

What is a null (amorphic) mutation?

back 10

It is the COMPLETE loss of gene function as compared to wild type. ex: a pigment that was brown know no longer produces color.

front 11

What is a leaky (hypomorphic) mutation?

back 11

A partial loss of gene function

front 12

What is a dominant negative mutation?

back 12

When one mutation inactivates several parts of a protein complex

front 13

What are the gain of function mutations?

back 13

hypermorphic and neomorphic mutations

front 14

What is a hypermorphic mutation?

back 14

It occurs when a gene becomes more active than normal and it continues normal gene activity, but at a higher rate

front 15

What is a neomorphic mutation?

back 15

It occurs when a gene takes on a NOVEL, or completely new function.

front 16

What are sex limited traits?

back 16

They are on autosomes, but due to hormonal differences, are only expressed in one sex.

front 17

What are sex influenced traits?

back 17

They occur on autosomes, are expressed in BOTH sexes, but have
different inheritance patterns due to hormonal differences. ex; baldness in males

front 18

True or false. Sex limited and sex influenced traits are different from sex linked traits

back 18

true

front 19

What is penetrance?

back 19

It is the degree to which a genotype correlates with a phenotype

front 20

What is fully penetrant traits?

back 20

The genotype always corresponds with the phenotype

front 21

What are nonpenetrant traits?

back 21

They do not match genotypes and expected phenotypes. ex: when R is round and r is wrinkled, a rr plant is round

front 22

What are incompletely penetrant traits?

back 22

Traits that sometimes match genotypes and phenotypes and sometimes don’t

front 23

What is variable expressivity?

back 23

The same genotype can present in varying degrees. Ex: the NF1 traits with bumps

front 24

What factors play a large role in certain genes being expressed?

back 24

Environmental and epigenetic factors

front 25

What is gene environment interaction?

back 25

When the environment plays a role in regulating gene expression, which may contribute to this variable expressivity and incomplete penetrance

front 26

What is pleiotropy?

back 26

where one genotype causes multiple different phenotypes at once. ex: sickle cell causing different symptoms

front 27

What is polygenic inheritance?

back 27

occurs when multiple genotypes combine to code for one phenotype. ex: height being controlled by multiple gene interactions

front 28

What are epistasis interactions?

back 28

when one gene alters the expression of another gene

front 29

What are complementary gene interactions and its ratio?

back 29

Its when two genes together contribute to a given phenotype...(9:7 ratio)

front 30

What are duplicate gene action and its ratio?

back 30

Occurs when two genes are redundant of one another and only one genotype is required to produce the same phenotype... (15:1 ratio)

front 31

What are dominant gene interactions and its ratio?

back 31

occurs when a phenotype is present only when BOTH dominant alleles
are present, if only one is present there is a third phenotype... (9:6:1 ratio)

front 32

What is recessive epistasis and its ratio?

back 32

when a homozygous recessive genotype in one gene masks the expression of the second gene, regardless of what it is...(9:3:4)

front 33

What is dominant epistasis and its ratio?

back 33

when a dominant genotype in one gene masks the expression of the second gene, regardless of what it is...(12:3:1)

front 34

What is dominant suppression and its ratio?

back 34

when one dominant allele suppresses another dominant allele...(13:3)

front 35

What is genetic linkage?

back 35

It occurs when two genes are so close together, that their alleles segregate together instead of independently. It is a direct contradiction to Mendel’s law of independent assortment

front 36

What are synthetic genes?

back 36

Genes on the same chromosome

front 37

true or false. linked genes are always synthetic genes

back 37

true. (Genes that are closer together on the chromosome are typically more strongly linked together)

front 38

Can synthetic alleles undergo crossing over?

back 38

yes

front 39

What is nonrecombinant?

back 39

When the new chromosome contains the SAME alleles as originally (it looks like the parent chromosome)

front 40

What is recombinant?

back 40

When the new chromosome contains DIFFERENT alleles than originally (it looks different than the parent chromosome)

front 41

What is recombinant frequency?

back 41

It is how often linked genes recombine (undergo crossing over)

front 42

true or false. The closer two linked genes are, the LESS they will crossover, and the smaller “r” will be

back 42

true

front 43

is % r is equal to 1 map unit

back 43

yes

front 44

what is the recombination frequency?

back 44

number of recombinants/ total number of progeny

front 45

What organism do we use for test crossing?

back 45

a homozygous recessive organism. (important because only the recessive genes pass on)

front 46

Under no genetic linkage what ratio should you see?

back 46

1:1:1:1 phenotypic ratio

front 47

true or false. Under genetic linkage, you will see a much greater proportion of non-recombinant chromosomes

back 47

true

front 48

What other factors affect recombination frequency?

back 48

species, age, sex, environment, temperature

front 49

The homogametic sex has higher rates of what?

back 49

recombination across the WHOLE genome

front 50

Recombination is favored by what?

back 50

natural selection (provides species with more genetic diversity)

front 51

Does recombination happen at equal frequencies across the genome?

back 51

No (they have hotspots and coldspots)

front 52

What are Variable Number Tandem Repeats (VNTR)?

back 52

a genetic marker

short DNA sequences that repeat in a chromosomal region

front 53

What are Single Nucleotide Polymorphisms (SNPs)?

back 53

It is one of the most common genetic markers. They are substitutions in a SINGLE base pair and each person has a unique set in their genome

front 54

What are Restriction Length Fragment Polymorphisms (RFLP)?

back 54

genetic markers

They are changes in where restriction enzymes cut DNA at SPECIFIC spots

front 55

All of these genetic markers are inherited what?

back 55

codominantly

front 56

Sometimes SNPs can be inherited together in a pattern known as a what?

back 56

haplotype (it occurs when the SNPs are linked)

front 57

Why are haplotypes common in tracking ancestry?

back 57

Because a certain haplotype is more common in one ethnicity than another which is known as linkage disequilibrium

front 58

What is lod score analysis?

back 58

the way we calculate the probability of two genes being linked

front 59

The odds value is determined by what?

back 59

the likelihood CAUSED by linkage / likelihood by independent assortment

front 60

What is the theta value?

back 60

the likelihood of linkage for recombination frequencies

front 61

What does a theta value of 0 mean?

back 61

complete linkage

front 62

What does a theta value of 0.5 mean?

back 62

complete independent assortment

front 63

Scientist calculate a lod score form what?

back 63

the theta value

front 64

If a lod score is >3, then what?

back 64

there is likely genetic linkage

front 65

If a lod score is <-2, then what?

back 65

there is likely NOT genetic linkage

front 66

If a lod score is <3 and >-2, then what?

back 66

the test is inconclusive

front 67

What is a Genome Wide Association Study?

back 67

It finds influential genes across a genome (a gene that can influence a population)

front 68

Why do we typically preform GWAs?

back 68

to look for known haplotypes across the genome

front 69

GWAs are analyzed by what?

back 69

Manhatten plots (the higher a dot on a bar the stronger association between a gene and a disease)

front 70

What are Mendelian genes?

back 70

They are caused by a single gene change. can be dominant or recessive, and is passed down through families.

front 71

Chromosomal conditions results from?

back 71

changes in number of chromosomes, rearrangements, or changes in large sections of chromosomes

front 72

Chromosomal conditions are caused by errors in what?

back 72

meiotic cell division

front 73

What is carrier testing for?

back 73

Used in specific populations and for some prenatal tests. (those tested do not have symptoms)

front 74

What is presymptomatic testing?

back 74

Testing for genetic conditions with late age of onset. Ex: Huntington’s Disease

front 75

Newborn testing is required by who?

back 75

All US states and must be treated within a few weeks of life

front 76

What does prenatal testing do?

back 76

detects genetic conditions in a fetus

front 77

What are Chromosomal Territories?

back 77

The specific space in interphase where chromosomes are uncondensed and very active.

front 78

What are Interchromosomal domains?

back 78

are spaces between territories where molecules like enzymes can move. Usually more gene rich chromosomes are closer to the nucleus

front 79

Chromosome structure is visualized by what?

back 79

karyotypes

front 80

Karyotypes identify chromosomes by what?

back 80

their size and shape. (p-short arm and q-long arm)

front 81

How are banding patterns on chromosomes identified?

back 81

By Giemsa staining

front 82

What are euchromatin?

back 82

Regions of chromosomes that are lighter stained. (they are less condensed and more active in gene transcription)

front 83

What are heterochromatin?

back 83

Regions of chromosomes that stain darker. (They are less active in gene regulation and are more condensed)

front 84

true or false. Chromatin can stay one or they other or can switch

back 84

true

front 85

What is polyploidy?

back 85

occurs when there are 3+ sets of chromosomes in the nucleus of an
organism

front 86

What is autopolyploid?

back 86

occurs when there is a chromosomal set duplication within a species

front 87

What is allopolyploid?

back 87

happens when chromosomes sets are combined from different species

front 88

What does meiotic nondisjunction lead to?

back 88

diploid egg/sperm cells (results in a triploid organism)

front 89

What does mitotic nondisjunction lead to?

back 89

doubles chromosome number

front 90

What is hybrid vigor?

back 90

the increase in heterozygotes in hybrid lines. (Heterozygotes usually have better resistance to disease)

front 91

true or false. Nondisjunction is different from polyploidy

back 91

true

front 92

What does nondisjunction do?

back 92

It changes chromosome NUMBER, but not copies of chromosomes

front 93

Nondisjunction in meiosis I does what?

back 93

creates a offspring that has monosomes or trisomies

front 94

Nondisjunction in meiosis II does what?

back 94

only 2/4 gametes will be affected. 1 will be a trisomy, 1 will be a
monosomy, and 2 will be normal

front 95

Most nondisjunction in humans will not survive as humans, therefore they are sensitive to what?

back 95

gene dosage changes

front 96

What is trisomy 21?

back 96

Down syndrome with 3 copies of chromosome. (Caused by the DSCR region of the chromosome)

front 97

What is monosomy X?

back 97

Turner syndrome and there is only one X chromosome copy only found in females. There is Happloinsufficiency of SHOX gene

front 98

How does uniparental disomy occur?

back 98

when both chromosome copies are from the same parent

front 99

What is a break point on a chromosome?

back 99

when BOTH strands of DNA break at a given point

front 100

Terminal deletions occur where?

back 100

At the end of the chromosome and include the telomeres

front 101

Interstitial deletions occur where?

back 101

In the MIDDLE of a chromosome and require 2 break points

front 102

Whenever a chromosome fragment loses its centromere it becomes what?

back 102

acentric

front 103

Duplications and deletions can happen at what level?

back 103

micro and macro

front 104

What happens at the Macro level?

back 104

whole gene duplication, section of a chromosome deletion

front 105

What happens at the micro level?

back 105

single nucleotide deletion, gene fragment duplication. (the only possible detection is FISH staining)

front 106

What does unequal crossing leave us with what type of chromosome?

back 106

one recombinant chromosome with a duplication and the other recombinant chromosome with a deletion

front 107

When can inversions occur?

back 107

when a DNA sequence flips and is read backwards. Ex: the sequence ABCDE can become AEDCB

front 108

What is paracentric inversion?

back 108

inversions that occur ONLY on one arm of the chromosome and do not involve the centromere

front 109

What is pericentric iinversions?

back 109

They are inversions occurring across BOTH arms of the chromosome and involve the centromere

front 110

What is Nonreciprocal Translocations?

back 110

happen when a piece of DNA from one chromosome breaks off and attaches to a different chromosome

front 111

What is Reciprocal Translations?

back 111

occur when pieces of DNA from TWO different chromosomes swap placed. (can play a large role in infertility)

front 112

What is Robertstonian Translocations?

back 112

occur when two chromosomes fuse together (therefore the total number of chromosomes in the cell will drop)

front 113

In Eukaryotes, DNA is bound and organized by what?

back 113

histone proteins

front 114

What are nucleosomes?

back 114

The complex the DNA wraps around a histone octomer to form

front 115

What is the nucleosome core comprised of?

back 115

2 H2A proteins, 2 H2B proteins, 2 H3 proteins, and 2 H4 proteins

front 116

What is a chromatosome?

back 116

When the H1 histone protein binds to the nucleosome DNA and the complex is formed

front 117

What is linker DNA?

back 117

Chromatosomes that are separated by short pieces of DNA

front 118

What is a solenoid?

back 118

When chromatin further condenses to form a 30nm fiber

front 119

Why is the chromatin organization important?

back 119

Chromatin condensation helps regulate gene expression, and forming the chromosome shape helps equal chromosome separation in cell division

front 120

What is metacentric?

back 120

the middle of the chromosome

front 121

What is submetacentric?

back 121

the centromere is between the center and tip

front 122

Arocentric?

back 122

the centromere is close to the end. "satellite"

front 123

What is telocentric?

back 123

The centromere is at the tip of the chromosome and there is no p arm

front 124

What are the histone proteins?

back 124

H1, H2A, H2B, H3, H4

H1 is not on the nucleosome

front 125

BRCA1 and BRCA2 mutations increase the risk for what?

back 125

breast and ovarian cancer

front 126

Bayeson analysis determines what?

back 126

probability of a certain genotype in a family

front 127

What is a Mendelian condition?

back 127

caused by mutation of a single gene and has 6 patterns of inheritance

front 128

What are the observed 6 patterns of inheritance?

back 128

autosomal dominant, autosomal recessive, X-linked dominant,
X-linked recessive, Y-linked, and mitochondrial

front 129

What is a chromosomal condition?

back 129

caused by an extra chromosome, a missing chromosome, duplication or deletion of a chromosome segment. Usually, a result of new mutation in meiotic division.

An example is trisomy 21 (down syndrome)

front 130

What are multifactorial conditions?

back 130

influenced by multiple genes along with environmental factors; diabetes is an example

front 131

What are indicators for genetic testing?

back 131

previous child with a genetic or chromosome condition, family history of a genetic or chromosome condition, advanced maternal age or other indicator of elevated risk in pregnancy, fetal exposure to a toxic or harmful compound, prolonged infertility or repeated pregnancy loss, new diagnosis of a genetic or chromosome condition, consultation for pre- or -postgenetic or chromosome test risk assessment

front 132

What are the goals of genetic counseling?

back 132

Provide comprehensive information before or after a genetic tests, explain risk recurrence, identify the beliefs, values, and relationships that are affected, and provide referrals to support groups or services.

front 133

Four areas of investigation that are affected by the collection of personal genetic or genomic information.

back 133

Genetic Research, Genetic Health Care, Societal Issues of Genetics and Genomics, Legal, Regulatory, and Public Policy Issues

front 134

Genetic Counseling and Ethical Issues

back 134

Prenatal genetic and chromosome testing, Newborn genetic screening, and Testing for genetic predisposition