A2 inheritance (topic 7)

Question 1

genotype def

Answer 1

the genetic makeup of an organism

Question 2

phenotype def

Answer 2

the physical expression of a characteristic

Question 3

autosome def

Answer 3

chromosomes that aren’t sex chromosomes
=> we have 22 pairs / 44 autosomes

Question 4

monohybrid inheritance def

Answer 4

inheritance of a single gene, phenotype is controlled by a single gene
(punnett squares used)

Question 5

recessive def

Answer 5

only expressed in the phenotype if 2 copies are present in the genotype (homozygous recessive)

Question 6

codominance def (also called incomplete dominance)

Answer 6

when a dominant allele doesn’t completely mask effects of recessive allele so both are expressed in the phenotype (blended)

Question 7

sex linkage def

Answer 7

the expression of an allele dependent on your gender (because gene is located on sex chromosome)

most sex linked traits are located on X chromosome because Y doesn’t have an equivalent locus
=> females carry 2 alleles of sex linked gene, men carry 1

Question 8

dihybrid inheritance def

Answer 8

inheritance of 2 characteristics at the same time

Question 9

chi squared test - what kinds of data used and what’s it used for

Answer 9

large sample size 20+

categorical data (nominal)

only raw numbers (not %)

=> used to compare actual result with expected ratios

Question 10

chi squared degree of freedom =

Answer 10

number of categories -1

Question 11

if sum of chi-squared is less than critical value then you ____ the null hypothesis

Answer 11

accept

(so results are due to chance)

Question 12

variation in a species due to

Answer 12

mutations
meiosis, random fertilisation of gametes during sexual reproduction

environment - climate conditions

Question 13

environment factors that limit population is called

Answer 13

selection pressures
=> predation, disease, and competition

Question 14

process of evolution by natural selection depend on:

Answer 14

• organisms producing offspring that can be supported by amount of food, light, space
• genetic variation
• variety of phenotypes that selection operates against

Question 15

3 main types of selection

Answer 15

stabilising selection - preserves average phenotypes (against extremes)
=> baby weights (most successful characteristic)

directional selection - preserves one extreme from the mean
=> mean moves in that direction eg bacterial resistance

disruptive selection - both extremes are favoured over the mean
=> large mammals survive without food due to increased body fat, small mammals have decreased need for food

Question 16

Hardy Weinberg equation

Answer 16

p^2 + 2pq + q^2 = 1

p = frequency of dominant allele
q = frequency of recessive allele

Question 17

what points does the hardy weinberg principle assume

Answer 17

• no mutations
• no migration of alleles in/out population
• large population
• no selection, so every gene has chance of being passed down
• mating is random

Question 18

speciation def

Answer 18

how new species arise after a population becomes separated and cannot interbreed

Question 19

allopatric speciation

Answer 19

caused by physical separation -> as groups become separated and reproductively isolated, natural selection occurs to adapt to where they live until they are no longer able to interbreed and become separate species

Question 20

sympatric speciation

Answer 20

same geographical area: new species evolve from a single ancestral species due to a chromosomal error during cell division that leads to reproductive isolation.

also could be mutations that courtship behaviour isn’t recognised or anatomical changes eg big dog small dog