Lecture 14 Human Genetics

Question 1

Describe what is meant by a mendelian disease

Answer 1

Monogenic disease

Question 2

State the 4 modes of mendelian inheritance

Answer 2

Autosomal dominant
Autosomal recessive
X linked recessive
X linked dominant

Question 3

Give three reasons as to why the mode of inheritance can’t always be deduced from pedigree analysis

Answer 3

• Incomplete dominance
• Delayed onset such as that observed in Huntingtons disease
• Genetic Heterogeneity

Question 4

Define genetic heterogeneity

Answer 4

A single disease can be caused by mutations in different genes.

Question 5

Define DNA marker

Answer 5

a genetic marker in a gene or DNA sequence is a gene with a known location on a chromosome that can be used to identify individuals or species. A genetic marker can be a short DNA sequence,like an SNP or a long one like in minisatellites.

Question 6

Explain what a Haplotype is

Answer 6

Collection of alleles in a cluster of tightly linked genes on a chromosome that are likely to be inherited together.

Question 7

What is a Single nucleotide polymorphism

Answer 7

A single base change. This results in variation in the DNA sequence between two members. The two sequences differ by one single base.

Question 8

What is a short tandem repeat

Answer 8

also known as a microsatellite. This is a tract of repetetie DNA in which certain DNA motifs are repeated a varying number of times. These microsatellites occur at thousands of locations in a persons genome.
STRs represent regions of high variablity between individuals

Question 9

How are STR’s used in forensic analysis

Answer 9

• STRs are highly variable regions between two peoples DNA.
• employ PCR to amplify the sample to produce a large enough sample size for analysis by gel electropheresis
• DNA is separated via gel electropheresis to give a unique DNA banding profile.

Question 10

What is meant by positional cloning

Answer 10

This is a lab technique used to identify the position of a disease associated gene along the chromosome

Question 11

Summarise the process of positional cloning

Answer 11

• most common procedure for isolating genes that pre-dispose one to a certain disease
• process is initiated by mapping the responsible gene to its location on a chromosome linked to a disease.
• then clone this region to isolate the candidate genes
• finally identify the mutation by mutational analysis to single out the correct gene.