Cell division and Genetics/Inheritance - Tutorial 6

Question 1

Define the terms, alleles, homozygous alleles & heterozygous alleles

Answer 1

• Alleles - are alternative versions of a gene
• Homozygous alleles - have identical information for a trait
• Heterozygous alleles - have different information for a trait

Question 2

Name & describe the two different types of cell division

Answer 2

Somatic cell division:
- Aim is to replicate cells to replace dead or injured cells or add new cells during tissue growth
- Occurs through mitosis and cytokinesis

Reproductive cell division:
- Aim is to produce the gamete cells (sperm and oocyte) required for the next generation
Occurs through meiosis

Question 3

Explain how genetic variation occurs

Answer 3

Crossing over increases genetic variation, occurs in meiosis and is the exchange of genes between homologous (paired) chromosomes

Question 4

Define cancer and the terms malignant & benign tumours

Answer 4

Cancer: is the group of diseases that results from uncontrolled or abnormal cell proliferation

Malignant: Malignant tumours undergo metastases (the spread of cancerous cells to other parts of the body)

Benign tumours do not metastasise (they do not spread)

Question 5

Name the type of cancer that arises from the following tissues

Answer 5

Epithelial tissue - Carcinoma Melanocytes - Melanoma Lymphatic tissue - Lymphoma
Leukocytes - Leukaemia

Question 6

State three causes of cancer

Answer 6

• Environmental agents, eg. Chemicals and radiation
• Viruses, eg. human papillomavirus (HPV) causes cervical cancer by stimulating abnormal proliferation of cells
• Genes, eg. abnormalities of the genes that control and regulate cell division

Question 7

Define the following terms; inheritance, genetics, genotype, phenotype, mutation, autosomes & x-linked (sex) chromosomes

Answer 7

Inheritance - passing of genetic traits to another generation

Genetics - branch of biology that deals with inheritance

Genotype - genetic makeup of an individual

Phenotype - Physical characteristics of an individual, determined by genotype and environment

Mutation - permanent change in a gene

Autosomes - any chromosome other than sex chromosomes

Sex chromosomes - the 23rd pair of chromosomes females have XX and males have XY

Question 8

Define multiple allele inheritance and give one example of a genetic trait
carried by this type of inheritance

Answer 8

• Genes with more than two alternate forms
  Example: 3 different alleles of the I gene, IA, IB or i

Question 9

Define complex inheritance and give one example of a genetic trait carried by
this type of inheritance

Answer 9

• Most inherited traits are not controlled by on gene but by: the combined effects of two or more genes or combined effects of many genes and environmental factors

-Height: malnutrition, disease

Question 10

Describe the difference between autosomes & sex chromosomes

Answer 10

• Autosomes - are any chromosomes other than a sex chromosomes
• Sex chromosomes - are the 23rd pair
  In females, the 23rd pair consists of XX
  In males, the 23rd pair consists of XY

Question 11

Explain why many x-linked conditions primarily affect males

Answer 11

More common in men as they have only one X chromosome

Question 12

Give two examples of x-linked conditions

Answer 12

• Haemophilia
• Colour Blindness

Question 13

Explain the terms trisomy & monosomy and give an example of a condition for
each

Answer 13

Trisomy: 2n+1, has an extra chromosome, down syndrome

Monosomy: 2n-1, is missing a chromosome, turner syndrome