Genetic Inheritance

Question 1

Phenotype

Answer 1

physical manifestation of a genetic trait

not just what you see with your eyes, but could be something cellular as well

Question 2

Genotype

Answer 2

the combination of genes responsible for a phenotype

Question 3

Dominant Alleles

Answer 3

only one copy necessary for the phenotype to be expressed

represented with capital letters

Question 4

How are genes inherited?

Answer 4

Every cell, and thus, every gene, has two copies, one copy from your mom and one from your dad - but the copies might not have the same alleles, however, have the same genes
The copies of the same chromosomes are know as homologues
each person inherits two alleles for every gene - one maternally, one paternally
except for sex chromosomes

Question 5

Locus

Answer 5

the location of a gene on a chromosome

genes can be describes in terms of their loci

Question 6

Recessive Alleles

Answer 6

both alleles must be recessive for it to be expressed

Question 7

Gain of function mutation

Answer 7

the mutation makes the protein do something it couldn’t do before
tend to be dominant

Question 8

Loss of function mutation

Answer 8

protein can’t do something it can do before as result of mutation
typically recessive

Question 9

Homozygous

Answer 9

two copies of same allele (RR, rr)

Question 10

Heterozygous

Answer 10

what you get when you cross a homozygous recessive and homozygous dominant
one recessive and one dominant allele

Question 11

Hemizygous

Answer 11

only one copy of an allele is present
occurs with genes on X and Y chromosomes
also nondisjunction with organism with aneupoloidy

Question 12

Self-cross Heterozygous

Answer 12

genotype: 1:2:1 ratio, 25% offspring homozygous dominant, 50% heterozygous, 25% homozygous recessive
phenotype: 3:1 ratio, 75% will show dominant phenotype, 25% will show recessive

Question 13

Test-cross

Answer 13

done to distinguish if a genotype is heterozygous or homozygous
done with a homozygous recessive
RR x rr = you’ll have all Rr, or dominant phenotype expressing offspring
Rr x rr - you’ll have 50% dominant expressing and 50% recessive expressing offspring

Question 14

Wild-type

Answer 14

default phenotype or genotype present in the most members of a species

Question 15

Codominance

Answer 15

when two dominant alleles can be expressed at the same time

example: human blood typing ABO, or dalmations (BW alleles)

Question 16

Incomplete Dominance

Answer 16

heterozygote displays a blended phenotype

ex: snap dragon flower, dom = red, rec = white, hetero = pink

Question 17

Penetrance

Answer 17

likelihood that a carrier of a given genotype will manifest the corresponding phenotype
ex: BRCA1 gene - 80% risk of developing breast cancer, so 80% penetrance

Question 18

Expressivity

Answer 18

intensity or extent of variation in phenotype
how much of an effect does that mutation have on the phenotype, vs with penetrance it is, does it effect the phenotype or not, and how ofen?

Question 19

Dihybrid Cross

Answer 19

when you cross two heterozygotes for two different traits
offspring will have the characteristic distribution of 9/16 dual dominant, 6/16 one recessive trait (3/16 of one type of recessive allele, 3/16 with the other), 1/16 dual recessive
9:3:3:1

Question 20

Law of independent assortment

Answer 20

the law that there is no link between inheritance with an allele of one gene and the allele of a different gene
however, this is not the case, as links that are closer together are less likely to undergo recombination that those that are further apart during prophase I of meiosis

Question 21

What are the 3 components of a evolutionary system?

Answer 21

1. variations in population
2. mechanism for variations to be reproduced over time
3. environmental constraints that allow favorable variations to be reproduced more than others (aka differential reproduction)

Question 22

Gene pool

Answer 22

combined set all all genes/alleles in a population
used to describe the genetic status of a population
evolutionary success = increase representation of certain allele within the pool

Question 23

Hardy-Weinberg Equilibrium

Answer 23

used to model stable gene pools
only applies under these criteria:
1. organisms must be diploid and reproduce sexually
2. mating is random
3. populations size is very large
4. alleles randomly distributed by sex
5. no mutations occur
6. no migration into or out of population
represent by p + q = 1
where p and q are two different alleles within an entire population (gene pool)
when we square these, we are crossing them, and are able to come up with the different possible combinations of the alleles
p^2 + 2pq + q^2 = 1

Question 24

Stabilizing Selection

Answer 24

both extremes of a phenotype are selected against

Question 25

Directional selection

Answer 25

one extreme phenotype selected against

Question 26

Disruptive selection

Answer 26

median phenotype selected against

Question 27

Genetic drft

Answer 27

role of chance, in the absence of strong selective pressures, in determining reproductive fitness of various alleles

Question 28

Bottleneck effect

Answer 28

external event dramatically reduces size of population in a way that is random, so that the allele left over is just random in terms of survival
ex: a flood wipes out population indiscriminately