Test 1 (1-2)

gene

a region of DNA that specifies a particular protein or RNA

artificial selection

selective breeding of plants and animals for certain desired traits

self-fertilization

mating between gametes from the same individual

cross-fertilization

mating between gametes come from separate individuals

What are the advantages of using pea plants in Mendel’s breeding experiments?

obtain lots of offspring within a short period of time

discrete traits

clear-cut, distinct opposite traits such as yellow vs. purple flower colour

continuous traits

traits with intermediate phenotypes like height or skin colour

pure-breeding/true-breeding/inbred

individuals that carry specific parental characteristics that remain constant for generations because have been mated only to each other for many generations

antagonistic pairs

mating between individuals with dissimilar characteristics

hybrid

offpring of parents with antagonistic traits

reciprocal cross

reversed the characterisitics of the male and female parents

i.e. pollen from purple flower x egg from white flower

vs. pollen from white flower x egg from purple flower

monohybrid cross

mating between **homozygous** individuals for one gene that have antagonistic traits (TT x tt)

What is the result of a cross between purebreds?

all offspring looking like one parent (dominant)

What is the phenotypic ratio resulting of a cross between a monohybrid individuals?

3:1

allele

alternative forms of a gene

monohybrid

indivual having 2 different alleles of a single gene

Mendel’s law of segregation

the two allleles of each gene separate during gamete formation, then unite at **random** at fertilization

product rule

the probablity of 2 or more independent events occuring together is the product of the probability that each event will occur by itself

sum rule

the probability of event 1 **or** event 2 occuring (mutually exclusive events) is the sum of their individual probabilities

How can you distinguish between a TT and Tt in plants?

self-fertilize and observe next generation

testcross

mating between individual with dominant phenotype (Y_) with recessive individual (yy) to find the **genotype** of the dominant individual

dihybrid

individual that is heterozygous for 2 genes (YyRr)

parental type

phenotype that looks like one of the parents

recombinant type

phenotype that does not resemble either of the parents

What is the phenotypic ratios for dihybrid crosses?

9:3:3:1

law on independent assortment

the alleles of 2 different genes gets sorted into gametes independently of each other

mutation

chance alteration of genetic sequence

wild-type allele (+)

an allele that is present in the population at a frequency higher than 1%

mutant allele

an allele that is present in the population at a frequency lower than 1%

Can a mutant allele become a wild-type allele?

yes - if it becomes common enough in the population (more than 1%)

monomorphic

a gene with only one common, wild-type allele present in the population (Agouti in mice)

polymorphic

a gene that has more than one common allele in the population (other alleles are very rare) (ABO blood type)

common variants

the high-frequency alleles of a polymorphic gene (HLA gene)

Human civilization is driven by

a) domestication in genetic process

b) cross-breeding experiments

c) Mendel’s genetics

a

How can we tell species apart?

same genes, different possible alleles

individuals that are genetically close enough to breed and produce fertile offspring

There is a concrete definition for species. T/F

F

The genotype of an individual is the sole influencer of phenotypes. T/F

F - can also vary based on environmental factors (e.g. UV radiation and skin colour)

The parental (P) generation…

a) just refers to the furthest most generation in a pedigree/breeding experiment

b) must always be pure breeding

c) must always be pure breeding for all traits

d) all of the above

b

The parent generation…

a) just refers to the furthest most generation in a pedigree/breeding experiment

b) must always be pure breeding

c) must always be pure breeding for all traits

d) the generation prior to the offspring of interest

e) all of the above

d

Discrete units of inheritance are _____

a) genes

b) genotypes

c) phenotypes

d) alleles

d

Genes/alleles are always designated by _____ (differentiate from when we refer to protein product)

italics

different alleles differ in _____ _____, this can result in the amino acid sequence of the protein or the _____ of the protein being made

nucleotide sequence, amount

What is the genotypic ratio for a cross between monohybrids?

1:2:1

What is the phenotypic ratio of the cross between dihybrids?

9:3:3:1

What must you NOT assume iof the parental generation of a dihybrid?

do NOT assume that the parentals are homozygous dom/dom x rec/rec

* can also be GG ww x gg WW

When dihybrids (2 genes) are crossed and the alleles act in simple dominant/recessive manner, new phenotypic _____ appear (not present in previous generations

combinations

In a test cross, you always want to mate the individual with the unknown genotype with an indvidual that is ___ ___

homozygous recessive

incomplete dominance

heterozygote does not resemble either homozygous parents, phenotype is an intermediate between the two pure-bred parents

What is the phenotypic ratio of a cross between monohybrids, acting in an incomplete dominance manner?

1:2:1

Traits that act in an incomplete dominance manner often relate to _____ _____

gene dosage

codominant

both traits of the parents show up equally in the heterozygote’s phenotype

What is the phenotypic ratio of a cross between monohybrids, acting in an co-dominance manner?

1:2:1

In complete dominance, the recessive alleles are most often _____, while dominant alleles are usually _____

nonfunctional, functional

when both alleles specify a functional gene product, they are often _____ for traits analyzed at the molecular level

co-dominant

ABO blood type is an example of which mode of inheritance, specifically IA and IB?

co-dominance

An allele that is dominant will always be dominant in any case. T/F

F - dominance or recessive is always relative to a second allele (i.e. in ABO blood type, IA is dominant over i, but co-dominant with IB)

dominance series

alleles are listed in order from most dominant to most recessive

In the case of multiple alleles, how can you tell that they are the result of different alleles of the same gene and not multiple genes?

all test pairings of alleles will yield a 3:1 ratio in the F2 generation

pleiotropy

a single gene determining a number of distinct traits

syndrome

a group of problems that are usually seen together

recessive lethal allele

in homozygous, the recessive lethal alleles will cause death

What is the phenotypic ratio involving recessive lethal allele between 2 monohybrids?

2:1

Recessive lethal mutations are common in animals including humans, however they often remain hidden, except in rare cases of homozygosity often caused by _____ mating

consanguineous

Recessive alleles causing prenatal or early childhood lethality canbe passed on to subseuqent generations only by _____ carriers because affected homozygotes die before they can mate

heterozygous

What are the phenotypic classes of 2 genes interacting additively on one gene? (complete dominance)

1. both present (A_ B_)
2. one present (A_ bb)
3. the other present (aa B_)
4. neither present (aa bb)

A cross between 2 heterozygotes (that came from pure-bred parents) resulted in a phenotypic ratio of 9:3:3:1. However, there are new phenotypes that were not present in prior generations. What is the most likely explanation for this?

2 genes (A and B) acting on one phenotype but are assorting independently and operation in indepedent biochemical pathways

epistasis

a gene interation in which an allele of one gene masks the effects of another gene’s alleles

In epistasis, the allele that is doing the masking is _____ to the gene that is being mask, the _____ gene

epistatic, hypostatic

recessive epistasis

homozygosity for a recessive allele of one gene hides tthe effect of a second gene

What is the phenotypic ratio for recessive epistasis?

9:3:4

The yellow coat colour in Labrador retriever and the Bombay phenotype is an example of which mode of inheritance?

recessive epistasis

reciprocal recessive epistasis

dominant alleles of two genes acting together produce the trait (A_ B_), while the other 3 phenotypic classes (A_ bb, aa B_, aa bb) do not

* aa is epistasis to gene B
* bb is epistasis to gene A

dominant epistasis

epistasis in which the dominant allele of one gene hides the effects of another gene

What is/are the possible phenotypic ratio for dominant epistasis?

12:3:1 or 13:3

heterogenous trait

a mutation at any one of a number of genes can give rise to the same phenotype

Two deaf parents can have hearing offspring if the nother and father are homozygous for recessive mutions in:

a) the same gene

b) different genes

b

What does complementation mean?

the original mutations affected two different genes, for both genes, the normal allele from one parent covered up for what the mutant allele fot eh same gene couldn’t provide (from the other parent)

* 2 deaf parents have mutations on different genes but their children have normal hearing
* this is because they have mutations on different genes and therefore the other parent’s allele “covered up” for the non-functional mutant allele (still making the protein needed for hearing)

penetrance

the proportion of individuals with a particular genotype who actually show the expected phenotype

* incomplete penetrance - ie. only 75% of people with the genotype for Retinoblastoma actually develop the disease

Which of the following are used to describe penetrance?

a) complete/incomplete

b) variable/unvarying

a

Expressivity

the degree/intensity in which a particular genotype is expressed in a phenotype

Which of the following are used to describe expressivity?

a) complete/incomplete

b) variable/unvarying

b

modifier genes

unline the major genes that have the main effects on the phenotype, modifier genes have a subtle, secondary effect

* ie. tail size in mice T causes short tail but other modifier genes can influence the effect on how much this allele will affect the actual size of the tail

temperature sensitive

the expressiblity of an allele is affected by temperature

conditional lethal allele

allele that only causes death only under certain conditions

permissive conditions

the conditions range where the conditional lethal allele does not cause death

restrictive conditions

the conditions where the conditional lethal allele will cause death

sex-limited traits

affect a structure or process that is found in only ONE sex (but not the other)

sex-influenced traits

show up in both sexes, but may differ between the sexes

Propose 2 scenarios for type of inheritance for coat colour? What are the expected phenotypic ratios for each case?

complete dominance (3:1) or incomplete dominance (1:2:1)

If an offspring has a different phenotype than hte parents, the parents cannot be _____, they must be _____

pure-breeding, heterozygous

A pure-breeding white goat and a pure-breeding black goat are bred together several times and all offspring are grey. This result indicates:

a) complete dominance

b) codominance

c) incomplete dominance

d) two genes interacting

c

Is colouring in zebras a result of codominance?

no - then there must exist zebras that are all black or all white

When establishing dominance series for a polymorphic gene, the crosses must be done with _____ individuals!

pure-breeding

Mutations is also known as _____ _____ in which there is a change in DNA sequence of a gene

chance alternations

The wild-type allele is always dominant, that’s why it’s the most common in the population. T/F

F

multifactorial inheritance/phenotype

a phenotype that arise from the action of more than 1 gene (polygenic) or frm interactions between genes and the environment

complementary gene action

two or more genes work in a process (biochemical pathway) to produce a particular trait

A phenotypic ratio of 9:7 indicates that there are _____ genes acting on the same phenotype

2 (modification of (9:3:3:1)

complementation testing is used for:

1)

2)

1) is 1 or 2 (or more) genes acting on the phenotype?

2) is the mutation on the same gene for both parents?

Rr Pp x Rr Pp involves 2 genes that act on one phenotype, this is an example of a dihybrid cross. T/F

F - dihybrid means that the they are heterozygotes for 2 genes that are acting on two different phenotypes