A gene has a certain nucleotide sequence that makes up a person's genotype. If this sequence changes via a mutation, it can result in variation in genotypes and the proteins produced. This in turn can change the characteristics of a population. During meiosis, homologous chromosomes pair up and can undergo crossing over, followed by two cell divisions that produce four haploid cells. This process contributes to genetic variability.

1. How variability is
produced in
populations
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2. 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.
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3. 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
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4. 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
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