What are the 2 forms of dominance?

Incomplete and codominance

What is incomplete dominance?

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

What is codominance?

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

What are lethal alleles?

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

What is a recessive lethal allele?

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

What are dominant lethal alleles?

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

What can lethal alleles cause?

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

What is happlosufficency?

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

What is happloinsufficency?

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

What is a null (amorphic) mutation?

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

What is a leaky (hypomorphic) mutation?

A partial loss of gene function

What is a dominant negative mutation?

When one mutation inactivates several parts of a protein complex

What are the gain of function mutations?

hypermorphic and neomorphic mutations

What is a hypermorphic mutation?

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

What is a neomorphic mutation?

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

What are sex limited traits?

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

What are sex influenced traits?

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

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

true

What is penetrance?

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

What is fully penetrant traits?

The genotype always corresponds with the phenotype

What are nonpenetrant traits?

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

What are incompletely penetrant traits?

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

What is variable expressivity?

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

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

Environmental and epigenetic factors

What is gene environment interaction?

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

What is pleiotropy?

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

What is polygenic inheritance?

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

What are epistasis interactions?

when one gene alters the expression of another gene

What are complementary gene interactions and its ratio?

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

What are duplicate gene action and its ratio?

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

What are dominant gene interactions and its ratio?

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)

What is recessive epistasis and its ratio?

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

What is dominant epistasis and its ratio?

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

What is dominant suppression and its ratio?

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

What is genetic linkage?

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

What are synthetic genes?

Genes on the same chromosome

true or false. linked genes are always synthetic genes

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

Can synthetic alleles undergo crossing over?

yes

What is nonrecombinant?

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

What is recombinant?

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

What is recombinant frequency?

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

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

true

is % r is equal to 1 map unit

yes

what is the recombination frequency?

number of recombinants/ total number of progeny

What organism do we use for test crossing?

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

Under no genetic linkage what ratio should you see?

1:1:1:1 phenotypic ratio

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

true

What other factors affect recombination frequency?

species, age, sex, environment, temperature

The homogametic sex has higher rates of what?

recombination across the WHOLE genome

Recombination is favored by what?

natural selection (provides species with more genetic diversity)

Does recombination happen at equal frequencies across the genome?

No (they have hotspots and coldspots)

What are Variable Number Tandem Repeats (VNTR)?

a genetic marker

short DNA sequences that repeat in a chromosomal region

What are Single Nucleotide Polymorphisms (SNPs)?

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

What are Restriction Length Fragment Polymorphisms (RFLP)?

genetic markers

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

All of these genetic markers are inherited what?

codominantly

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

haplotype (it occurs when the SNPs are linked)

Why are haplotypes common in tracking ancestry?

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

What is lod score analysis?

the way we calculate the probability of two genes being linked

The odds value is determined by what?

the likelihood CAUSED by linkage / likelihood by independent assortment

What is the theta value?

the likelihood of linkage for recombination frequencies

What does a theta value of 0 mean?

complete linkage

What does a theta value of 0.5 mean?

complete independent assortment

Scientist calculate a lod score form what?

the theta value

If a lod score is >3, then what?

there is likely genetic linkage

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

there is likely NOT genetic linkage

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

the test is inconclusive

What is a Genome Wide Association Study?

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

Why do we typically preform GWAs?

to look for known haplotypes across the genome

GWAs are analyzed by what?

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

What are Mendelian genes?

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

Chromosomal conditions results from?

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

Chromosomal conditions are caused by errors in what?

meiotic cell division

What is carrier testing for?

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

What is presymptomatic testing?

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

Newborn testing is required by who?

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

What does prenatal testing do?

detects genetic conditions in a fetus

What are Chromosomal Territories?

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

What are Interchromosomal domains?

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

Chromosome structure is visualized by what?

karyotypes

Karyotypes identify chromosomes by what?

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

How are banding patterns on chromosomes identified?

By Giemsa staining

What are euchromatin?

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

What are heterochromatin?

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

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

true

What is polyploidy?

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

What is autopolyploid?

occurs when there is a chromosomal set duplication within a species

What is allopolyploid?

happens when chromosomes sets are combined from different species

What does meiotic nondisjunction lead to?

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

What does mitotic nondisjunction lead to?

doubles chromosome number

What is hybrid vigor?

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

true or false. Nondisjunction is different from polyploidy

true

What does nondisjunction do?

It changes chromosome NUMBER, but not copies of chromosomes

Nondisjunction in meiosis I does what?

creates a offspring that has monosomes or trisomies

Nondisjunction in meiosis II does what?

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

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

gene dosage changes

What is trisomy 21?

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

What is monosomy X?

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

How does uniparental disomy occur?

when both chromosome copies are from the same parent

What is a break point on a chromosome?

when BOTH strands of DNA break at a given point

Terminal deletions occur where?

At the end of the chromosome and include the telomeres

Interstitial deletions occur where?

In the MIDDLE of a chromosome and require 2 break points

Whenever a chromosome fragment loses its centromere it becomes what?

acentric

Duplications and deletions can happen at what level?

micro and macro

What happens at the Macro level?

whole gene duplication, section of a chromosome deletion

What happens at the micro level?

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

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

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

When can inversions occur?

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

What is paracentric inversion?

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

What is pericentric iinversions?

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

What is Nonreciprocal Translocations?

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

What is Reciprocal Translations?

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

What is Robertstonian Translocations?

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

In Eukaryotes, DNA is bound and organized by what?

histone proteins

What are nucleosomes?

The complex the DNA wraps around a histone octomer to form

What is the nucleosome core comprised of?

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

What is a chromatosome?

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

What is linker DNA?

Chromatosomes that are separated by short pieces of DNA

What is a solenoid?

When chromatin further condenses to form a 30nm fiber

Why is the chromatin organization important?

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

What is metacentric?

the middle of the chromosome

What is submetacentric?

the centromere is between the center and tip

Arocentric?

the centromere is close to the end. "satellite"

What is telocentric?

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

What are the histone proteins?

H1, H2A, H2B, H3, H4

H1 is not on the nucleosome

BRCA1 and BRCA2 mutations increase the risk for what?

breast and ovarian cancer

Bayeson analysis determines what?

probability of a certain genotype in a family

What is a Mendelian condition?

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

What are the observed 6 patterns of inheritance?

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

What is a chromosomal condition?

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)

What are multifactorial conditions?

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

What are indicators for genetic testing?

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

What are the goals of genetic counseling?

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.

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

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

Genetic Counseling and Ethical Issues

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