How variability is produced in populations

1Tuesday, 22 November 11

Explain the consequence of a base substitution mutation in relation to the processes of transcription and

• A gene has a certain nucleotide sequence that makes up the genotype of a person. If this nucleotide sequence is changed in any way, there will be a variation in the genotypes and the proteins that the genes can produce. This will change the population of the species.

2Tuesday, 22 November 11

Define genotype, phenotype, dominant allele, recessive allele, codominant alleles, locus, homozygous, heterozygous, carrier and test cross.

Determine the genotypes and phenotypes of the offspring of a monohybrid cross using a Punnett grid.

• “A” is the dominant allele that shows as a phenotype whether the genotype is heterozygous or homozygous.

“a” is the recessive allele that is only shown as a phenotype when the genotype is homozygous recessive.Heterozygous is when there are both dominant and recessive alleles in the genotype.Homozygous is when there is two of the same type of allele in the genotype.

Let’s say that “A” stands for black eyes dominant allele and “a” stands for green eyes recessive allele.

A a

A AA black Aa black

a Aa black aa green

3Tuesday, 22 November 11

Outline the process of meiosis, including pairing of homologous chromosomes and crossing over, followed by two divisions, which results in four haploid cells.

• Crossing over --> in crossing over, the tips of the chromosomes cross during prophase. After “crossing over,” the chromosomes share the gene so that one chromosome would have a part of the other chromosome.

Another variability in metaphase ! --> the chromosomes that make up the homologous pair is randomly assorted.! ! ! ! ! --> through independent assortment, the homologous pairs are independently assorted along the equator of the cell.During fertilization, the choosing of the egg and the sperm is random

4Tuesday, 22 November 11