Year 10 T2 W4 L2 Worksheet - Inheritance

Describe the difference between males and females in terms of the number of X and Y chromosomes they have.

Why are certain genetic conditions more common in males than in females?

How does having two X chromosomes provide a "backup" for females in terms of expressing certain traits?

Discuss the advantages females have in terms of sex-linked inheritance compared to males.

What does the term "carrier" mean in the context of sex-linked traits?

Discuss the role of carriers in passing on sex-linked traits to their children.

Checking understanding: Of the 23 pairs of chromosomes that are found in the nucleus of human cells, one pair is not fully homologous. Which pair of chromosomes is this and why are they not fully homologous?

When writing the ​ (a)   of an individual in a sex-linked characteristic, you must show the sex ​ (b)   (to represent ​ (c)   ) as well as the alleles.

• genotype
• phenotype
• chromosomes
• gender

A ​ (a)   contains 2 ​ (b)   whilst a ​ (c)   only contains 1 ​ (d)   .

• genotype

• alleles

• gamete

• allele

• chromosome, genes, DNA, gene

• phenotype, traits, cell, trait

• nucleus, cells, nucleus, cell

• mitosis, chromosomes, meiosis, chromosome

• RNA, proteins, DNA, protein

Answer explanation

A genotype refers to the genetic makeup of an organism, which is represented by alleles. A gamete carries half the genetic information, hence containing only one allele. Therefore, the correct choices are genotype, alleles, gamete, and allele.

When writing genotypes in sex-linked chromosomes, we write a:

1) Heterozygous female as ​ (a)  

2) A male sufferer as ​ (b)  

• XCXc

• XCY

• XXY

• XX

• XY

• XYY

Answer explanation

In sex-linked chromosomes, a heterozygous female is denoted as XCXc and a male sufferer is denoted as XCY.