Lecture 08

Question 1

The two business ends of tRNA

Answer 1

1) the anticodon forms hydrogen bonds with the mRNA codon

2) the 3’ end binds the amino acid specified by the mRNA codon

Question 2

What controls gene expression in bacteria?

Answer 2

Oerson

Question 3

What controls gene expression in more complex organisms?

Answer 3

transcription factors and links genome to environment

Question 4

About how many transcription factors in humans

Answer 4

~2,000

Question 5

What are the steps of transcription?

Answer 5

1) Initiation
2) Elongation
3) Termination

Question 6

Transcription initiation

Answer 6

a cascade of transcription factors bind to the promoter region of a gene
-these open a pocket allowing the RNA polymerase to bind just in front of the start of the gene sequence

Question 7

Transcription elongation

Answer 7

RNA polymerase reads the nucleotides on the template strand from 3’ to 5’ and creates an RNA molecule that looks like the coding strand

Question 8

Transcription termination

Answer 8

occurs when sequences in the DNA prompt the RNA polymerase to fall off ending the transcript

Question 9

Translation

Answer 9

the process of reading the mRNA base sequence and creating the amino acid sequence of a protein
-occurs on the ribosome

Question 10

The genetic code

Answer 10

there are 64 codons, including:

• one start signal (AUG)
• three stop signals (UAA, UAG, and UGA)

Question 11

Genome sequences orientation

Answer 11

From short p-arm to long q-arm and in a 5’ to 3’ direction

Question 12

Forward and Reverse oriented gene transcript

Answer 12

• FWD oriented - its coding strand is on the plus strand of the genome sequence
• REV oriented - it’s on the minus strand

Question 13

Protein-encoding gene controls and the two general processes

Answer 13

• Promoter sequence (mutations)
• Extra copies of gene

Processes

1) Chromatin remodeling = “on/off” switch
2) microRNAs = “Dimmer” switch

Question 14

Chromatin remodeling - Three major types of small molecules that bind to histones (major role in gene expression)

Answer 14

Chromatin remodeling: transcription off –> (groups) transcription on

1) Acetyl group
2) Methyl groups
3) Phosphate groups

Question 15

microRNAs

Answer 15

• Belong to a class of molecules called noncoding RNAs
• 21-22 bases long
• human genome ~1,000 distinct microRNAs that regulate at least 1/3 of the protein-encoding genes

Question 16

What happens when a microRNA binds to a “target” mRNA

Answer 16

• It prevents translation

- It can also tag the mRNA for degradation

Question 17

Maximizing genetic info

Answer 17

The 20,325 genes in the human genome encode ~100,000 mRNAs, which in turn specify more than a million proteins

the “genes in pieces” pattern of exons and introns and alternate splicing help to greatly expand the gene number

proteins > (outnumber) genes

Question 18

Multifactorial traits

Answer 18

• caused by multiple factors including both genetic influences and environmental influences
• usually polygenic (influenced by many gene) w/ incomplete penetrance

Question 19

Studying multifactorial traits - quantitative genetics

Answer 19

attempts to determine the relative contribution of genes versus environment (heritability) to the trait variation observed in a population (e.g., nature vs. nurture)

Question 20

empiric risk

Answer 20

measures the probability that a trait will recur/occur based solely on observations

Question 21

incidence

Answer 21

the rate at which a certain event occurs (e.g., new cases/year)

Question 22

prevalence

Answer 22

the proportion or number of individuals who have a particular trait at a specific time (e.g., total cases)

Question 23

heritability

Answer 23

estimates the proportion of the phenotype variation in a population due to genetic differences