Chapter 15 - Genetic Monohybrid Crosses

Question 1

What is a monohybrid cross?

Answer 1

A monohybrid cross involves observing the inheritance of one character determined by one gene and therefore termed a monogenic trait.
When gametes are formed in a heterozygous individual, the alleles segregate to that each gamete is equally likely to contain either allele.
One only member of each homologous pair of chromosomes is present in each gamete so only allele of each gene is present in the gamete.

Question 2

How do sex linked genes affect inheritance?

Answer 2

Females have 2 X chromosomes and therefore have 2 copies of each gene carried n the X chromosome.
Males have 1 X chromosome and therefore have 1 copy of each gene carried on the X chromosome.

Question 3

What does co dominant refer to?

Answer 3

This is the relationship between two alleles of a gene, such that the heterozygous organism shows the expression of both alleles in the phenotype.

Question 4

What can affect the outcome of crosses?

Answer 4

• the results of punnet squares are the expected proportion of genotypes and phenotypes in a large sample. This is called the theoretical ratio.
• results in small sample space are more likely to deviate from the theoretical ideal due to chance events, sampling error and randomness of meiosis and fertilisation.
• meiosis all the combinations of alleles are distributed to gametes with equal probability. Any difference is due to chance combinations of alleles in gametes
• fertilisation of one pair of gametes is independent to another pair, chance events.