W5 Intro to Genetic diseases

Question 1

What is the phenotype?

Answer 1

Individuals observable traits (height, eye colour)
Physical expression of genotype

Question 2

What is the Genotype

Answer 2

The set of genes in our DNA which are responsible for a particular trait

Question 3

What is meant by true breed?

Answer 3

The kind of breeding wherein the parents would produce offspring that would carry the SAME phenotype

e.g When the plants self-pollinate, all their offspring are of the same variety

Question 4

What is meant by hybridisation?
What is a Monohybrid cross

Answer 4

-Mating, or crossing, of two varieties
-A cross between two parents that breed true for different versions of a single trait

Question 5

Homozygous definition

Answer 5

2 identical alleles

Question 6

Heterozygous

Answer 6

2 different alleles

Question 7

Monohybrid inheritance F2 generation ratio:

Answer 7

9:3:3:1

Question 8

What is the genome
What is an allele?

Answer 8

All the genes of an organism
Variations of a gene

Question 9

PP or pp is a what pair of alleles?

Answer 9

Homozygous

Question 10

What is a genetic disease?

Answer 10

Caused by an abnormality in an individual’s DNA. Most genetic disorders are quite rare
May/may not be inherited

Question 11

How does a non-heritable genetic disorder occur?

Answer 11

Defects may be caused by somatic mutations - changes to the DNA of somatic cells after the birth

The defect can only be heritable if genetic disorder occurs in the germ line

Question 12

What are the 4 types of genetic disorders?

Answer 12

1. Single gene defects
2. Chromosome abnormalities
3. Multifactorial disorders
4. Cancer

Question 13

What is a gene?

Answer 13

Unit of heredity. Encodes the synthesis of a gene product. Usually a protein or RNA.
(small section of DNA)

Question 14

What are the different mechanisms of inheritance? (3)

Answer 14

Autosomal dominant
Autosomal recessive
X-linked recessive or dominant

Question 15

What is a Frameshift mutation?

Answer 15

insertion or deletion of one or more bases causing the alteration of the reading frame of the gene and a different set of codons, leading to an altered protein.

Question 16

What type of disorder is sickle cell anaemia? (single gene defect)
Caused by what?

Answer 16

Autosomal recessive disorder
Caused by homozygosity (both alleles)- Point mutation in the beta-globin gene within chromosome 11

Question 17

How are red blood cells affected for sickle cell anaemia?

Answer 17

Normal
Disease

Question 18

Mendel- Pea experiment
F1 offspring?
F2 offspring?

Answer 18

100% yellow pea plants
75% yellow pea and 25% green pea (3:1)

Question 19

Which allele dictates the organisms phenotype?

Answer 19

The dominant allele

Question 20

Mendel’s third postulate:
Describe Independent segregation

Answer 20

During the formation of gametes, two copies (alleles) of each gene present in the parent separate so that each gamete receives only one allele for each trait

During fertilisation, a sperm cell carrying one or other allele fuses with an egg cell carrying one of the alleles to produce a zygote with two alleles

Question 21

What is Albinism?

Answer 21

A disorder (recessive) that results in little or no production of the pigment melanin, (colour of the skin, hair and eyes)

Question 22

How does a non-heritable genetic disorder occur?

Answer 22

Defects may be caused by somatic mutations - changes to the DNA of somatic cells after the birth

Question 23

What is a single gene disorder?

Answer 23

A disease caused by changes or mutations that occur in the DNA sequence of a single gene

Question 24

What is autosomal dominant?

Answer 24

If a single mutated allele is sufficient to cause the disease (heterozygosis)

Question 25

What is autosomal recessive?

Answer 25

If both mutated allele must be inherited to be affected (homozygosis)

Question 26

What is X-linked recessive or dominant?

Answer 26

mutated gene is present on the X chromosome

Question 27

What is a Missense mutation?

Answer 27

These are base changes that alter the codon for an amino acid resulting in its replacement with a different amino acid.

Question 28

What is a Nonsense mutation?

Answer 28

Base changes that convert an amino acid codon to a stop codon, resulting in a premature termination of translation and the production of a shortened protein.

Question 29

What is a silent mutation?

Answer 29

Do not cause any change in an amino acid

Question 30

What do Promoter mutations or mutations on other regulatory sequences do?

Answer 30

Affect the way gene transcription is regulated, often abnormally reducing or enhancing the expression of certain genes

Question 31

What is the difference between a Normal RBC and a Sickle RBC?

Answer 31

Normal:
1.Red blood cells shaped like a disk
2.Haemoglobin (protein) carries oxygen to all parts of the body

Sickle:
1.Red blood cells form an abnormal crescent shape
2.Haemoglobin (protein) is abnormally shaped
3.Don’t move easily through your blood vessels
4.Form clumps and get stuck in the blood vessels

Question 32

What is cystic fibrosis? (single gene defect)
How is it caused?

Answer 32

Autosomal recessive disease
-Mucus secretions accumulate in the lungs which block the airways, cause persistent infections and permanent lung damage

-Homozygosity (both alleles) for a point missense mutation in the CFTR gene within the chromosome 7

Question 33

What is Huntington’s disease?(single gene defect)

Answer 33

autosomal dominant disease
-Heterozygosity (1 defective allele) in the huntingtin gene located on chromosome 4
-Neurodegenerative disease

Question 34

What is Duchenne muscular dystrophy? (single gene defect)

Answer 34

• X-linked recessive disorder (DMD gene)
  -Males suffer progressive weakening of the muscles
• Males can’t be carriers

Question 35

Chromosome abnormalities:
What are Numerical Abnormalities?
What are Structural Abnormalities?

Answer 35

1. When an individual is missing either a chromosome from a pair (monosomy) or has more than two chromosomes of a pair (trisomy)
2. When the chromosome’s structure is altered