Chapter 8: Gene expression

Question 1

What is a genome?

Answer 1

All genetic material contained in an organism

Question 2

What is a polypeptide?

Answer 2

A polymer of many amino acids linked by peptide bonds

Question 3

What determines the amino acid assembled into polypeptides at ribosomes?

Answer 3

Nucleotide base pairs (A) adenine, (T) thymine, (C) cytosine and (G) guanine

Question 4

How many base pair combinations make up an amino acid?

Answer 4

64 total combinations.

Question 5

What is a codon?

Answer 5

A series of 3 nucleotide baes pairs in DNA and mRNA

Question 6

Where are polypeptide instructions kept?

Answer 6

DNA

Question 7

What makes polypeptides?

Answer 7

Ribosomes

Question 8

What is messenger RNA (mRNA)?

Answer 8

Carries instructions out of the nucleus into the cytoplasm where ribosomes attach

Question 9

How is mRNA generated?

Answer 9

Unwound DNA double helix

Question 10

What is transcription?

Answer 10

First step in producing mRNA

Question 11

What does RNA stand have that DNA doesn’t?

Answer 11

uracil (U) and pairs with A

Question 12

What is the first step in transcription?

Answer 12

gene unwinds, then unzips exposing nucleotide bases

Question 13

What is the other strand called that is not the template strand inn mRNA?

Answer 13

non-template or complementary strand

Question 14

What joins RNA strand to template strand?

Answer 14

RNA polymerase enzyme

Question 15

What happens after all nucleotide pairs are join in mRNA?

Answer 15

mRNA is released a single strand, the DNA zips up again and twist into double helix

Question 16

What is pre-mRNA?

Answer 16

unmodified mRNA that contains introns (Still in nucleus )

Question 17

Why are introns removed from mRNA?

Answer 17

They do not code for polypeptide production

Question 18

What does allow for polypeptide production in mRNA?

Answer 18

exons

Question 19

What is the process of removing introns and doing exons called?

Answer 19

Splicing

Question 20

What occurs after splicing?

Answer 20

mRNA is mature and moves out of nucleus

Question 21

What creates different types pf polypeptides?

Answer 21

Exons being spliced together differently

Question 22

How does ribosomes start translating mRNA?

Answer 22

Once it reaches start codon

Question 23

What is translation?

Answer 23

Joining of amino acids in specific order read from mRNA by ribosomes

Question 24

What is tRNA?

Answer 24

A RNA molecule which picks up amino acids in cytoplasm which then carries them to specific mRNA for polypeptide synthesis.`

Question 25

What shape is tRNA and why?

Answer 25

A clover shape to all anticodons to join nucleotide bases with mRNA

Question 26

What is a anticodon?

Answer 26

A sequence of 3 nucleotide bases complementary to mRNA

Question 27

Where do amino acids bind to tRNA?

Answer 27

Amino acid binding site opposite to anticodon

Question 28

How does amino acids pass from tRNA to mRNA?

Answer 28

When anticodons bond to complementary on mRNA, the amino acids at the binding site are joined to chain of amino acids by peptide bond

Question 29

When does ribosomes stop moving down mRNA?

Answer 29

When it comes to a stop codon

Question 30

What happens to tRNA and mRNA?

Answer 30

tRNA is peeled off and goes and collects more amino acids and mRNA is broken down enabling the RNA to be used again.

Question 31

What are the steps of mRNA?

Answer 31

DNA transcribed into mRNA modified into mature mRNA and is translated into proteins

Question 32

What is coding DNA?

Answer 32

Small part of the DNA used as a template for mRNA (code for polypeptides, less than 2%)

Question 33

What is non-coding DNA?

Answer 33

DNA not used for mRNA, 98% of DNA

Question 34

What does non-coding DNA do?

Answer 34

Switches genes on and off (regulating genes that are active in cells)

Question 35

What is a centromere?

Answer 35

Hold duplicated chromosomes (sister chromatids) together and are so the site at which spindle fibres move to chromosomes in cell division

Question 36

What is a telomere?

Answer 36

Extension of DNA which prolongs the life of chromosomes

Question 37

What is gene expression?

Answer 37

The process in which information is encoded in genes for polypeptides and thus protein synthesis

Question 38

How is the process of gene expression regulated?

Answer 38

The process allows certain genes to be expressed in certain cells at required times and rates.

Question 39

What are the factors that regulate the phenotypic expression of genes?

Answer 39

Chemical modification of chromatin at transcription stage; direct chemical modification of DNA at transcription stage; products of other genes at transcription; environmental factors; passed through offspring and translation stage (Remember - proteins bindings to specific DNA (translation and transcription phase), products of other genes and environmental exposure)

Question 40

How does chemical modification of chromatin at the transcription stage regulate phenotypic expression of genes?

Answer 40

When transcription occurs, DNA is wrapped very tightly and DNA polymerase cannot access the DNA and therefore the gene is switched off. Chemical modification (e.g. histone methylation) can unwrap the DNA causing the gene to be switched on.

Question 41

How does the direct chemical modification of DNA at the transcription stage regulate phenotypic expression of genes?

Answer 41

methylation and acetylation to either disable or stimulate the transcription of DNA

Question 42

How do the products of other genes at transcription regulate phenotypic expression of genes?

Answer 42

Activating proteins bind to non-coding DNA to unwind the histone proteins which allow the gene to be expressed.

Question 43

How do environmental factors affect the phenotypic expression of genes?

Answer 43

Environmental factors the organism is exposed to after birth. Twins have the same genes yet can display different phenotypic expressions.

Question 44

What are homeobox genes?

Answer 44

The genes responsible that regulate the body formation and patterning in developing an embryo. They are activated by specific concentrations of positional proteins e.g. Bicoid protein

Question 45

What regulates differentiation for tissue formation and morphology?

Answer 45

Differential gene expression controlled by transcription factors

Question 46

What is an example of a transcription factor that regulates morphology?

Answer 46

Homeobox genes e.g. fruit fly has 13000 genes but only 8 determine its morphology.

Question 47

What is an example of a cell differentiation (determining of XY) that regulates morphology?

Answer 47

Need to know - (SRY Gene) is located on the arm of the Y chromosome. Once expressed, it produced testosterone influencing cellular development.