Lecture 08 Flashcards Preview

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Flashcards in Lecture 08 Deck (23):
1

The two business ends of tRNA

1) the anticodon forms hydrogen bonds with the mRNA codon
2) the 3' end binds the amino acid specified by the mRNA codon

2

What controls gene expression in bacteria?

Oerson

3

What controls gene expression in more complex organisms?

transcription factors and links genome to environment

4

About how many transcription factors in humans

~2,000

5

What are the steps of transcription?

1) Initiation
2) Elongation
3) Termination

6

Transcription initiation

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

7

Transcription elongation

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

8

Transcription termination

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

9

Translation

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

10

The genetic code

there are 64 codons, including:
-one start signal (AUG)
-three stop signals (UAA, UAG, and UGA)

11

Genome sequences orientation

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

12

Forward and Reverse oriented gene transcript

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

13

Protein-encoding gene controls and the two general processes

-Promoter sequence (mutations)
-Extra copies of gene

Processes
1) Chromatin remodeling = "on/off" switch
2) microRNAs = "Dimmer" switch

14

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

Chromatin remodeling: transcription off --> (groups) transcription on
1) Acetyl group
2) Methyl groups
3) Phosphate groups

15

microRNAs

-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

16

What happens when a microRNA binds to a "target" mRNA

-It prevents translation
-It can also tag the mRNA for degradation

17

Maximizing genetic info

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

18

Multifactorial traits

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

19

Studying multifactorial traits - quantitative genetics

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

20

empiric risk

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

21

incidence

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

22

prevalence

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

23

heritability

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