3.7 Inheritance

Question 1

define genotype

Answer 1

the genetic constitution of an organism

Question 2

phenotype

Answer 2

the expression of this genetic constitution and its interaction with the environment

Question 3

gene

Answer 3

a length of DNA that is a sequence of nucleotide bases which code for a particular polypeptide

Question 4

allele

Answer 4

one of the different forms of a gene

Question 5

dominant

Answer 5

the allele of the heterozygote that expresses itself in the phenotype

Question 6

recessive

Answer 6

the allele of the heterozygote that is not expressed

Question 7

homozygous dominant

Answer 7

both alleles are dominant

Question 8

homozygous recessive

Answer 8

both alleles are recessive

Question 9

codominant

Answer 9

neither allele is recessive, both will be expressed in the heterozygote’s phenotype

Question 10

autosomes

Answer 10

the non-sex chromosomes, genes found here are chromosomal

Question 11

asymptomatic carriers

Answer 11

carry one of the recessive alleles so can pass onto offspring, no symptom

Question 12

monohybrid cross

Answer 12

shows the likelihood of different alleles of a gene being inherited by the offspring of certain parents

Question 13

genetic crosses show

Answer 13

the genotype of the parents, the gametes’ alleles and the offspring phenotype

Question 14

symbols for a codominant genetic cross

Answer 14

capital letters represent the genotype for the gene
superscript letters represent the alleles

Question 15

dihybrid crosses show

Answer 15

the combination of offspring for two unlinked genes
two genes with two alleles, four different gamete combinations
one allele on each side of the cross

Question 16

sex linkage, problems caused by it

Answer 16

The Y chromosome misses some matching genes on the X chromosome because X is longer.
There is a non homologous portion of the X chromosome.
This means recessive characteristics on the non homologous section of the X chromosome are more frequent in males (XX) because there is no chance of a dominant allele on Y to express itself.

Question 17

define autosomal linkage

Answer 17

two or more genes are carried on the same autosome

Question 18

explain autosomal linkage

Answer 18

Genes on the same autosome are linked because during independent segregation of meiosis 1 they stay together. Closer together, less likely to split.

Question 19

define epistasis

Answer 19

When the allele of one gene affects or masks the expression of another in the phenotype.
If the allele is recessive, 2 copies will be needed to block its’ expression.

Question 20

criteria to use chi squared

Answer 20

Sample size is relatively large, over 20
Data falls into discrete categories
Raw counts used, no percentages or rates
Comparing experimental results with theoretical ones

Question 21

what does chi squared tell you

Answer 21

if observed results were statistically different to your expected results.
Must be compared to a critical value.
A means of testing where any deviation between the observed and the expected numbers in an investigation is significant or not.

Question 22

null hypothesis

Answer 22

there is no significant difference between the two, any difference due to chance alone, so random

Question 23

alternative hypothesis

Answer 23

there is a significant difference between the two, so linked

Question 24

if chi result larger/equal to critical

Answer 24

reject null hypo, there is a significant link which is not due to chance

Question 25

if chi result lower than critical

Answer 25

accept null hypo, any link is due to chance alone

Question 26

degrees of freedom

Answer 26

number of categories minus one

Question 27

hardy weinberg principle

Answer 27

If certain conditions are met, the allele frequencies of a gene within a population will not change from one generation to the next

Question 28

necessary conditions

Answer 28

Diploid organism
Sexual reproduction ONLY
No overlap between generations (parents do not mate with their offspring)
Mating is random
Large population size
No migration, mutation or selection (no flow of alleles in or out and equally likely to be passed on to the next generation)

Question 29

when is HW useful

Answer 29

when building models/making predictions of how frequencies will change in future generations

Question 30

equation for allele freq

Answer 30

p + q = 1

Question 31

equation for genotype freq

Answer 31

P2 + 2pq + q2 = 1

Question 32

p and q represent..

Answer 32

p is dominant
q is recessive