7A

Question 1

what is monohybrid inheritance?

Answer 1

inheritance of a characteristic controlled by a single gene

Question 2

monohybrid crosses

Answer 2

shows the likelihood of the different alleles of that gene being inherited by their offspring

Question 3

phenotypic ratios

Answer 3

the phenotypic ratio is the ratio of different phenotypes in the offspring - although sometimes you won’t get the predicted ratio, as the alleles could be codominant or sex-linked

Question 4

what is a Punnett square?

Answer 4

a way of showing a genetic diagram

Question 5

what is co-dominance?

Answer 5

both alleles are expressed in their phenotype as neither alleles are recessive (E.g. sickle cell anaemia - a mutation in the haemoglobin gene)

Question 6

monohybrid cross of two heterozygous parents, what ratio do you expect?

Answer 6

1 : 2 : 1

Question 7

Dihybrid

Answer 7

the inheritance of two genes simultaneously (E.g. flowers colour and leaf shape)

Question 8

multiple allele crosses

Answer 8

multiple alleles crossed, E.g. blood types O, A, B, AB - crossing a parent with alleles A O, and a parent with alleles B O, gives a expected ratio of 1 : 1 : 1 : 1

Question 9

with heterozygous Dihybrid crosses, the ratio you expect is

Answer 9

9 : 3 : 3 : 1

Question 10

sex linked characteristics

Answer 10

alleles coding for certain characteristics are located on the sex chromosome

Question 11

how are men more likely to inherit a sex linked disease? E.g. colour blindness, haemophilia

Answer 11

because the Y chromosome is smaller than the X, it only takes one allele to code for a characteristic, unlike women who need either two recessive alleles (or a dominant) men only need one recessive allele. Y-linked disorders do exist but are less common

Question 12

when a male without colourblindness and a female carrier have offspring, what do you expect?

Answer 12

only the males in the offspring will be at risk, as the females won’t have the other allele (From their dad) to make them colour blind, they would only be a carrier

Question 13

linkage of autosomal genes

Answer 13

Genes on the same autosome are said to be linked as they don’t separate during independent segregation (Meiosis 1). Only when crossing over occurs they can be split. The closer the genes are together on the autosome, the more likely they are said to be linked as its less likely crossing over will split them up

Question 14

linkage of autosomal gene ratio

Answer 14

phenotypic ratio is not like the dihybrid cross (9:3:3:1), but more like the monohybrid cross ratio (3:1) as they’re inherited together, meaning they’re more likely to inherit their parents heterozygous genotype and phenotype

Question 15

linkage of autosomal gene example: two parents, one homozygous dominant for red eyes and wing length (NNRR) and one homozygous recessive for vestigial wing and purple eyes (nnrr) what offspring and ratio do you expect?

Answer 15

offspring were all heterozygous for normal wing and red eyes (NnRr)

Question 16

linkage of autosomal gene example 2: the heterozygous parent for normal wing and red eyes (NnRr) was crossed with a homozygous recessive vestigial wing with purple eyes (nnrr) what is the expected ratio of offspring?

Answer 16

1 : 1 : 1 : 1 4 Normal wings, red eyes 4 normal wings, purple eyes 4 vestigial wings, red eyes 4 vestigial wings, purple eyes

Question 17

what is epistasis?

Answer 17

many different allele can control the same characteristic. this is because the allele of one gene masks/blocks the expression of another allele

Question 18

what is chi squared?

Answer 18

chi squared is a statistical test used to see if the results of an experiment support a theory

Question 19

what always is the null hypothesis for a chi squared experiment?

Answer 19

There is no significant difference between the observed and expected results

Question 20

what is the chi squared formula?

Answer 20

Question 21

What is a critical value?

Answer 21

The critical value compares the X² value with the critical values to determine the properbility that the difference between the expected and observed is due to chance

Question 22

if the chi squared value is larger than the critical value, what do you do?

Answer 22

reject the null hypothesis

Question 23

if the chi squared value is lower than the critical value, what do you do?

Answer 23

fail to reject (Accept) the null hypothesis