Mandelian genetics
What is a gene?
A discrete unit of genetic code
Name four characteristics Gregor Mendel observed when studying pea plants
-seed shape
-seed colour
-Flower colour
-Pod shape
-Pod colour
-flower position
-stem height
What is a characteristic?
A distinct heritable feature, such as flower color, that varies among individuals.
What is a trait?
A variant of a characteristic, such as a lily being purple or white.
Mendel chose to use true-breeding varieties of pea plants for his studies. What is a true-breeding variety?
plants that produce offspring of the same variety when they self-pollinate
What is hybridization?
When two different true-breeding varieties are crossed.
True-breeding parents are __ generation
P
Hybrid offspring of P generation are called __ generation
F 1
When F1 individuals self-pollinate or cross- pollinate with other F1 hybrids, __ generation is produced
F 2
What is a dominant trait?
A trait that will be overpowering in the phenotype.
What is a recessive trait?
A trait that can be easily overpowered in the phenotype unless no dominant trait is present.
An allele codes for different variations of a _______. Each resides at specific locus on a specific ____________.
gene, chromosome
For each characteristic an organism inherits (minimum) ____ alleles. One from each parent
2
Two alleles at a particular locus of the chromosome will code for the same characteristic although they may or may not code for the same trait. True or false?
True. For example, the two alleles may both code for flower colour. They may code for the same flower colour or two different ones.
In punnet squares a __________ ___________ represents a dominant allele, and a _________ _________ represents a recessive allele
capital letter, lowercase letter
An organism with two identical alleles for a character is _____________
homozygous
An organism that has two different alleles for a gene is _______________
heterozygous
Could you consider heterozygous plants true-breeding?
No
What is the difference between a phenotype and a genotype?
A phenotype is what you see and a genotype is what's in the genes
In the example of feather colour in chickens, BB and Bb chicken have the same ________ (black), but different____________
phenotype, genotypes
What is a testcross?
A breeding tactic used to determine a mystery genotype by cross-breeding the individual with a homozygous recessive individual
F1 indivuduals heterozygous for one character were called ________________ in Mendel's experiments
monohybrids
A cross between two heterozygotes is called a _____________ cross
monohybrid
Crossing two true-breeding parents differing in two characters produces __________ (heterozygous for both characters)
dihybrids
dihybrid cross be?
To determine if two characters are transmitted as a package or independently
What is the law of independent assortment?
The law of independent assortment states that each pair of alleles segregates independently during gamete formation
What situation might the law of independent assortment not hold true in?
When two genes are really close on the same chromosome
What is the multiplication rule?
The multiplication rule states that the probability that two or more independent events will occur together is the product of individual probabilities
What is the addition rule
The addition rule states that the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities
For example: ¼ + ¼ = ½
Applying multiplication and addition rules a dihybrid cross is equivalent to ______ or ______ independent monohybrid crosses occurring simultaneously
two or more
Basic principles of segregation and independent assortment apply even to more complex patterns of inheritance, true or false?
true
What is the difference between complete dominance, incomplete dominance and codominance?
Dominant alleles are more prevalent in the population. Ture or false?
False, six fingers/toes is dominant but rare
The four phenotypes of the ABO blood group in humans are determined by _______ alleles
three: A AB B O are four combinations of the same three alleles
How many possible genotypes are there for a person with blood type O?
1
What is the heterozygous blood type genotype in humans?
AB
The trait that blood types code for is the ___________ on the outside of the blood cell
carbohydrates
Blood type AB has _____ different carbohydrates on the cells whereas blood type O has _______
two, zero
What is pleiotropy?
Pleiotropy is a property where genes have multiple phenotypic effects
In epistasis, a gene at one locus alters the ___________ _____________ of a gene at a second locus.
For example, in Labrador retrievers and many other mammals, coat colour depends on two genes
phenotypic expression
What are Quantitative characters?
those that vary in the population along a continuum
What is indicates polygenic inheritance?
an additive effect of two or more genes on a single phenotype like skin colour in humans
What is the norm of reaction?
the phenotypic range of a genotype influenced by environment
When genetic and environmental factors collectively influence phenotype of a character it is said to be __________
Multifactoral
What is a pedigree?
a family tree describing interrelationships of parents and children across generations
Why are pedigrees relevant to genetics?
Because Inheritance patterns of particular traits can be traced and described using pedigrees and they can be used to make predictions about future offspring
What is a carrier?
are heterozygous individuals who carry the recessive allele but are phenotypically normal
Mating between close relatives decreases the chances of two mating between two carriers of the same allele, true or false?
False
Amniocentesis and chorionic villus sampling (CVS) are both examples of what kind of test?
Prenatal fetal testing for genetic disorders