Week 26 - Genetics introduction and basic concepts

Question 1

Orthologous

Answer 1

Not only related by descent but have the same function

Question 2

Paralogous

Answer 2

Originate from the same ancestor but have different functions (diverged)

Question 3

Pseudogene

Answer 3

Non-functional sections of DNA that look like functional sections.
Usually copies of genes that have muted and changed over generations.

Question 4

Analogous

Answer 4

High similarity by chance or covergent evolution

Question 5

Homologous

Answer 5

Related by descent, same gene but different species

Question 6

Haploid/ Diploid

Answer 6

Haploid - One copy of each gene
Diploid - Two copies of each gene (one maternal, one paternal)

Question 7

Genotype

Answer 7

Specific allele composition

Question 8

Phenotype

Answer 8

‘the form that is seen’

Question 9

Haplotype

Answer 9

DNA variations (polymorphisms) that tend to be inherited

Question 10

What is the word when the heterozygote has a greater chance of survival than either homozygote?

Answer 10

Heterotic balancing selection
Eg. Sickle cell trait: the heterozyote protects from malarial infection

Question 11

Codominance

Answer 11

When both alleles contribute to the phenotype

Question 12

Incomplete dominance

Answer 12

When the dominant allele doesn’t completely mask the resessive allele traits

Question 13

Below is the DNA sequence of wild type beta-globun encoding the first 10 amino acids of the HBB protein. Sickle cell replaces the 7th amino acid Glu for Val.

ATG GTG CAC CTG ACT CCT GAG GAG AAG TCT

What is the likely sequence of the beta sickle cell allele?

Answer 13

GTG - check this

Question 14

What is a missense mutation?

Answer 14

When a sequence change causes a change in amino acid - can be a big or small change

Question 15

What is a frame shift mutation?

Answer 15

Insertion or deletion of nucleotides in the code - not a multiple of 3

Question 16

What is a nonsense mutation?

Answer 16

When a sequence change codes for a stop codon instead of a codon specifying an amino acid

Question 17

What are the three main mechanisms of spontaneous mutation?

Answer 17

Bp substitution, frame shift, deletion/ insertion

Question 18

Epistasis

Answer 18

Gene interactions that affect the phenotype - whenever two or more genes interact to create a new phenotype/ trait (instead of masking each other eg dominant/ recessive)

Question 19

Karyotype

Answer 19

The appearance of a complete set of chromosomes. Includes: size, numbers, shapes.

Question 20

The 3rd position is the ‘loosest’ in terms of binding to the cognate tRNA. What would you call it?

Answer 20

The most genetically degenerate, they are the least important