Intro to Genetics

Question 1

How many chromosomes does the normal human genome have?

Answer 1

23 Autosomes & 1 pair of sex chromosomes

Question 2

What do genes do?

Answer 2

Sections of a chromosome that code to make a protein

Question 3

What are non-coding regions responsible for?

Answer 3

Chromosome structural integrity and regulation

Question 4

How many genes do we have?

Answer 4

20,000

Question 5

What are the 3 types of genetic disease?

Answer 5

• Single Gene
• Chromosomal
• Multifactorial

Question 6

What does the OCA2 gene do?

Answer 6

Gives instruction for a protein called P Protein & are located in melanocytes which produce melanin (pigmentation)

Question 7

Where is the OCA2 gene?

Answer 7

OCA2 gene is on chromosome 15

Question 8

What can happen if there’s a single gene mutation?

Answer 8

If there is a change in the genetic code (Base pairs G-C/A-T) this can affect the instructions given to the enzyme. Sometimes these are physiological which can code for eye colour and some of these changes are pathological changes which leads to significant reduction in pigmentation.

Question 9

What is a geneotype?

Answer 9

Genetic make up of the individual (OCA2)

Question 10

What is a Phenotype?

Answer 10

Observable characteristics of the individual (i.e. Albinism)

Question 11

What factors can cause variability in single gene mutations?

Answer 11

1) Other factors influence expression of gene

A) Age-related cumulative frequency
B) Environmental factors
C) Polygenic Factors
D) Epigenetics – parent-of-origin and imprinting

2) Differences in the location of the genetic mutation

Question 12

What does it mean if there are chromosomal mutations that change the number or structure?

Answer 12

• Aneuploidy: - abnormal number of Chromosomes
• Normal Human Genome has 46 Chromosomes
• Can be significantly more detrimental than single gene mutations.

Question 13

What does it mean for chromosomal mutations to be multi-factorial?

Answer 13

• Do not follow a simple Mendelian pattern (not normally distributed throughout the population)
• Environment factors increase or decrease risk
• Occurs frequently in one gender more than the other
• Occurs more frequently in specific ethnic groups

Question 14

What are the 5 types of inheritance?

Answer 14

• Dominant
• Recessive
• X-linked Recessive
• X-linked Dominant
• Mitrochondrial

Question 15

What does it mean for inheritance of a gene to be autosomal dominant?

Answer 15

• Only one parent is needed to carry the mutated gene
• Affected children will more often have an affected parent
• Usually observed in every generation
• Male-to-male transmission most common
• 50% chance of inheriting if parent is affected
• A new mutation can spontaneously occur (De Novo)

Question 16

What does it look like for inheritance to be autosomal recessive?

Answer 16

• 2 copies are required from either parent
• Parents can be unaffected but carriers
• Can skip generations
• More common in consanguineous families (where couples are related)
• Carriers (heterozygotes) are usually unaffected
• 2 carriers having a child = 25% risk of child affected

Question 17

What does it mean for inheritance to be X-linked Recessive?

Answer 17

• Males affected more so than females
• Females rarely affected unless both inherited alleles are mutated
• Affected males cannot pass on their condition
• Only mothers can be carriers to their sons (not daughters)
• Males 50% chance of being affected if have a carrier mother

Question 18

What does it mean for inheritance to be mitochondrial?

Answer 18

• Affected females are also carriers of the mutation but not males
• Offspring, male or female, can be affected
• Affected males are not carriers so cannot pass to children

Question 19

Look at family trees

Question 20

What is Cyogenetics?

Answer 20

Study of chromosomal mutations

• Cell are obtained from the DNA sample, grown and stained
• Chromosomes extract and placed on slides where they are observed by microscope
• Look at the number and structure of the chromosomes
• Fluorescence in-situ hybridsation (FISH) can be used to look at the chromosomes more closely

Question 21

What is Molecular Genetics?

Answer 21

Study of single gene mutations

• Sequence of DNA code and observe for any changes
• too small to be observed under microscope so DNA has to be extracted and chemicals added to detect each base pair along the sequence
• this is then compared to the normal sequence and noted for mutations