T7: Genetics, Populations, Evolution + Ecosystems

Question 1

allele

Answer 1

one of the different forms of a gene

Question 2

genotype

Answer 2

the genetic makeup of an organism

Question 3

homologous chromsomes (pair)

Answer 3

a pair of chromosomes (maternal+paternal) that have the same loci in diploid organisms

Question 4

gene

Answer 4

a length of DNA that normally codes for a polypeptide

Question 5

pedigree charts

Answer 5

diagram representations of family trees that show patterns of inheritance
male - square + female - circle , shading means characteristic present in phenotype

Question 6

epistasis

Answer 6

when the allele of one gene affects or masks the expression of another in the organism, two genes interact together to affect the phenotype
e:g agouti mice

Question 7

linked genes / autosomal linkage

Answer 7

two or more genes carried on the same non-sex chromosome, explains why characteristics are often inherited together

Question 8

homozygous

Answer 8

two or more of the same alleles present on both homologous chromosomes

Question 9

loci

Answer 9

the position of a gene on a particular chromosome

Question 10

phenotype

Answer 10

the observable or biochemical characteristics of an organism

Question 11

recessive

Answer 11

an allele only expressed when present with an identical allele

Question 12

Mendel’s law of independent assortment

Answer 12

law that states that each member of a pair of alleles may combine randomly with either of another pair

Question 13

dihybrid crosses

Answer 13

inheritance patterns of two genes

Question 14

dominant

Answer 14

an allele always expressed in the phenotype that masks the expression of other alleles

Question 15

multiple alleles

Answer 15

a gene with more than two allelic forms

Question 16

chi squared

Answer 16

stats test that compares observed data with expected ratios

Question 17

null hypothesis

Answer 17

there is no significant difference between observed and expected values

if Mendel’s law applies then

Question 18

sex linked

Answer 18

a gene that is carried on both the X or Y chromosome

Question 19

co-dominant

Answer 19

two alleles are both expressed in the phenotype

Question 20

what do genetic diagrams look like?

Answer 20

must contain (F1 ) parent phenotype, parent genotype, gametes and punnet square

Question 21

4 conditions of Hardy weinberg?

Answer 21

Large population
No immigration or emigration
No mutations
No natural selection

Question 22

Formula for Hardy weinberg

Answer 22

P2+2pq+q2

P = homozygous dominant
2pq = heterozygous
Q = homozygous recessive

Question 23

Explain how natural selection occurs

Answer 23

Variation occurs due to mutations giving rise to new alleles
Selection pressure = struggle for survival
Some organisms have alleles that provide are advantageous so are more likely to survive and reproduce
They pass on their advantageous alleles to their offspring
The allele frequency in population increases over time

Question 24

Directional selection

Answer 24

Selective pressures favour individuals with a favourable combination of alleles one direction from the mean
Mean shifts in direction of phenotype

Question 25

Stabilising selection

Answer 25

Selective pressures favour the mean
Individuals with extreme phenotypes less likely to survive so SD gets smaller over time

Question 26

Disruptive selection

Answer 26

Selection against the mean
Favours both extremes of phenotypes
Could result in 2 separate species

Question 27

Speciation

Answer 27

Formation of a new species from an existing species

Reproductive separation of 2 populations can result in the accumulation of differences in their gene pools, new species arise when these 2 populations cant interbreed to produce fertile offspring

Question 28

Allopatric speciation

Answer 28

Geographical isolation separates the gene pools, no gene flow
Then evolution by natural selection occurs resulting in 2 species that can’t interbreed to produce fertile offspring

Question 29

Sympatric speciation

Answer 29

Populations in the same area

Question 30

Genetic drift

Answer 30

Allele frequencies change in a population due to chance factors
Stronger in small populations due to chance having a larger effect