3.7 Genetics, populations, evolution and ecosystems

Question 1

Define genotype and phenotype

Answer 1

Genotype:
genetic constitution of an organism.
-determines the limits within characteristics may vary between individuals

Phenotype:
expression of this genetic constitution and its interaction with the environment.

Question 2

sme key terms

Answer 2

The chromosomes of eukaryotic cells occur in homologous pairs (there are two copies of each chromosome)

As a result cells have two copies of every gene

As there are two copies of a gene present in an individual that means there can be different allele combinations within an individual

The genotype of an organism refers to the alleles of a gene possessed by that individual. The different alleles can be represented by letters

When the two allele copies are identical in an individual they are said to be homozygous

When the two allele copies are different in an individual they are said to be heterozygous

The genotype of an individual affects their phenotype

A phenotype is the observable characteristics of an organism

Question 3

Define dominant, recessive and codominant

Answer 3

dominant:
-alleles that are always expressed in the phenotype
-means they’re expressed in both homozgous and heteroxygous individuals

recessive:
-only expressed in the phenotype if no dominant allele is present
-means they’re only expressed in a homozygous individual

codominant:
-both alleles are expressed in the phenotype at the same time
-seen in heterozygous individuals
-e.g. blood type

Question 4

Define genes and alleles:

Answer 4

gene:
-sequence of DNA nucleotide bases that code for a particular protein
-
allele:
-different forms of a gene

Question 5

difference between homozygous and heterozygous

Answer 5

homozygous:
-alleles on each chromosome are the same in a pair of homologous chromosomes

heterozygous:
–alleles on each chromosome are different in a pair of homologous chromosomes

Question 6

Define homozygous dominant and homozygous recessive

Answer 6

Homozygous dominant:
-organism with 2 dominant alleles

Homozygous recessive
-organism with 2 recessive alleles

Question 7

Define sex-linkage

Answer 7

A gene whose locus is on the X chromosome

Question 8

Define autosomal linkage

Answer 8

Genes that are located on the same chromsome (not the sex-chromosomes

Means that alleles for each gene linked on the same chromosome will be inherited together

This impacts predicted gametes

Question 9

Define epistasis

Answer 9

When one gene modifies or masks the expression of a different gene at a different locus

Question 10

Define monohybrid and dihybrid

Answer 10

Monohybrid: genetic inheritance cross of a characteristic determined by one gene

Dihybrid: genetic inheritance cross for a characteristic determined by two genes

Question 11

Define the following:

gene pool
population
allele frequency

Answer 11

Gene pool: all the alleles of all the genes within a population at one time

Population: all the individuals of one species in one area at one time that can interbreed to make fertile offspring

Allele frequency: the proportion of an allele within the gene pool

Question 12

Describe how a chi-squared test should be carried out