Chromosomes, Genes & DNA

Question 1

What is genetics?

Answer 1

The study of inherited characteristics no the way they are passed from one generation to another.

Question 2

What are chromosomes?

Answer 2

Threadlike structures found in the nucleus of cells on which genetic material is organised.

Question 4

Describe the structure of DNA.

Answer 4

Each chromosome contains one double-stranded molecule. A molecule of DNA is made from two strands of nucleotides. Each nucleotide contains a nitrogenous base (adenine, thymine, guanine, cytosine), a sugar molecule and a phosphate group.

Question 5

What is meant by complimentary bases?

Answer 5

Nucleotides with adenine are always opposite with nucleotides with thymine, and cytosine is always opposite guanine.

Question 6

What is a gene?

Answer 6

A small section of DNA that codes for a particular protein to determine a feature, and is also known as a hereditary unit.

Question 7

What is an allele?

Answer 7

Each chromosome in a pair may carry an alternative form of the same gene. This alternative form is called an allele.

Question 8

What is a karyotype?

Answer 8

The number and appearance of all chromosomes in the nucleus of a cell of an individual organism.

Question 9

What is meant by a homologous pair of chromosomes?

Answer 9

Each chromosome has a matching pair that carries the same gene.

Question 10

What is a centromere?

Answer 10

It is a part of a chromosome which attached the two DNA molecules together.

Question 11

What is a mutation?

Answer 11

A change in the DNA of the cell. Mutations are caused by environmental pressures.

Question 12

What is meant by chromosomal mutation?

Answer 12

This occurs when the number of chromosomes is changed. For example, in Down Syndrome, the cells have 47 chromosomes instead of 46. There is an extra chromosome 21.

Question 13

What is meant by gene mutation?

Answer 13

This occurs when the structure of a DNA molecule forming a gene goes through certain changes. For example, in cystic fibrosis, a normal gene helps to keep the mucus in the alveoli, but if the gene is mutated, the mucus becomes thick. If a person has a mutated gene on both the chromosome, he or she will have a disease.

Question 14

What are mutagens?

Answer 14

Factors that cause mutations.

Question 15

What are four example of mutagens?

Answer 15

1) chemicals like tar in cigarette smoke and certain dyes in food
2) ultraviolet radiation
3) viruses
4) inheritance

Question 16

What happens if a mutation affects the functioning of a cell?

Answer 16

It results in the death of the cell and the mutation is lost.

Question 17

What happens if the mutation does not affect the functioning of the cell?

Answer 17

The cell divides and forms daughter cells with mutant genes. This mutation is also lost when the organism dies.

Question 18

How are genetic diseases caused?

Answer 18

Mutations in sex cells or cells that divide to form sex cells are passed onto the offspring.

Question 19

What is DNA (deoxyribose nucleic acid)?

Answer 19

It is the chemical that is the basis of inheritance.