Genetics

Question 1

Where is genetic code found and what does it do?

Answer 1

Contained within the chromosome inside nucleus of cells. Genetic instructing determines cell structure.

Question 2

How many chromosomes does a human somatic cell have?

Answer 2

23 pairs (except gametes).

Question 3

What is gene mutation?

Answer 3

A permeant heritable change in the one or more alleles that produce a different variant of the same trait (for example hair colour)

Question 4

What are some of the causes of gene mutation?

Answer 4

Chemical, radiation, physical, ageing

Question 5

What results from a gene mutation?

Answer 5

A mutation in the DNA will result in a change in the protein that the DNA codes for, which results in a change to cell structure

Question 6

Discuss the cystic fibrosis as a genetic condition.

Answer 6

Cycstic Fibrosis results from a gene mutation that affects the movement of water and salts across cell membranes. It results in defective respiratory and gastro systems where a thick sticky mucus builds up, blocking systems and causing repeated chest infection.

Question 7

Discuss muscular dystrophy as a genetic condition.

Answer 7

MD is caused by mutations in genes responsible for the structure and functioning of a persons muscles. Its a progressive condition and certain kinds of MD such as Duchenne shorten life.

Question 8

Discuss Huntingdons disease as a genetic condition.

Answer 8

Mutation that affects brain leading to muscle contractions, disability and depression. Occurs in middle aged male and is fatal after 20 years.

Question 9

Discuss Achondroplasia as a genetic condition.

Answer 9

Mutation that occurs when gametes are formed and is subsequently hereditary. Affects growth of upper arms and legs leading to dwarfism. Can cause bone and spinal development problems

Question 10

What is DNA composed of?

Answer 10

Nucleotides

Question 11

What are the four nucleotides?

Answer 11

Adenine
Guanine
Thymine
Cytosine

Question 12

How many nucleotides are in the human genome?

Answer 12

The Human genome project sequenced all 3.2 billion nucleotides and discovered there are around 30,000 genes in the human body. (gene is a distinct sequence of nucleotides)

Question 13

Each triplet of nucleotides will code for…

Answer 13

A specific Amino Acid, which alongside other AA’s will code for a specific protein

Question 14

A change in nucleotide sequence will therefore…

Answer 14

result in a change in protein synthesised and it may either be absent or altered. This is called an inborn error of metabolism.

Question 15

What is an inborn error of metabolism?

Answer 15

A rare genetic disorder that affects specific proteins that ordinarily breakdown food and metabolise it. One example is PKU.

Question 16

What is PKU?

Answer 16

Phenylkeontonuria. Due to a genetic mutation, the body cannot breakdown phenylalanine (common in meat and dairy). Phenylalanine therefore builds up and can cause brain damage

Question 17

If a person carries the gene defect but has no symptoms they are called a?

Answer 17

Carrier

Question 18

What are genotypes and phenotypes?

Answer 18

Genotypes - set of heritable genes

phenotype - visible gene determined characteristics

Question 19

Explain Homozygous and Heterozygous?

Answer 19

Homozygous = 2 identical copies of gene (BB or bb)
Heterzygous = 2 different copies of gene (Bb)

Question 20

What are sex linked disorders?

Answer 20

Genetic disorders that occur more frequently in one sex than the other.

Question 21

Sex linked disorders are more common in males, why?

Answer 21

Females have XX chromosomes and males have XY. This means if female has mutation on one chromosome she will be a carrier and if a male has on one chromosome he will have the disorder.