chapter 19 - genetics of living systems

Question 1

What are transcription factors?

Answer 1

• proteins that control the rate of protein synthesis by switching genes on and other genes off

Question 2

What is a promoter region?

Answer 2

• a short sequence of DNA at the start of a gene (the bit that dna / rna polymerase attaches to )

Question 3

How does a transcription factor(TF) help cause the gene to transcribe?

Answer 3

• TF moves from the cytoplasm into the nucleus
  -TF binds to the promoter region
• If TF is an activator, it will help rna polymerase to bind to the DNA resulting the gene being transcribed
• if TF is a repressor, it will prevent rna polymerase binding to the DNA as a result gene is not transcribed

Question 4

What are the two types of transcription factors?

Answer 4

• activators
• repressors

Question 5

What is the difference between regulator genes and structural genes?

Answer 5

• regulator genes make transcription factors that control the expression of other genes
• structural genes make proteins that function in a cell (e.g enzymes)

Question 6

How does the presence of lactose effect gene expression?

Answer 6

• if lactose is not present, the lac repressor protein binds to the operator
• this prevents the rna polymerase binding to the promoter region resulting in no transcription
• if lactose is present, it binds to the lac repressor protein changing its shape
• this removes the lac repressor protein from the operator
• rna polymerase binds to the promoter region
• structural genes are expressed
• enzymes are made(lactose permease)

Question 7

What are mutations

Answer 7

• A change to the nucleotide sequence of DNA
• they are mistakes made when replicating DNA(interphase)

Question 8

what are the 3 types of mutations with a brief explanation ?

Answer 8

• Substitution, one base in the dna sequence is swapped
• insertion, one base is added to the dna sequence
• deletion, one base is removed from the dna sequence

Question 9

What are the effects of the 3 types of mutations?

Answer 9

• substitution, can have no effect but chance of one amino acid being changed
• insertions and deletion, both lead to a frameshift (all the following triplets in a dna sequence are affected)

Question 10

What is the advantages and disadvanatages of mutations?

Answer 10

• advantage, causes a change that improves the function of the protein , increases survival or reproduction
• disadvantage, causes a change that makes a non functional protein, decreases survival or reproduction

Question 11

Explain the effect of a change to a single amino acid with regards to bonding and protein structure

Answer 11

• a change in one dna triplet causes a change in the translation of one amino acid
• this changes the primary structure of the protein
• this changes the hydrogen and ionic bonding
• this changes the tertiary structure of the protein

Question 12

Explain the effect of a change to the sequence of many amino acids with regards to bonding protein structure

Answer 12

• frame shift, changes all of the DNA triplets in a sequence
• changes the primary structure
• this changes the hydrogen and ionic bonding
• this changes the tertiary structure of the protein

Question 13

what is the difference between a homeobox gene and a homeodomain protein ?

Answer 13

• homeobox gene codes for homedomain protein
• homeodomain protein is a transcription factor

Question 14

Why is the homeobox gene highly conserved between species?

Answer 14

• as mutations would lead to changes in the body plan
• this would effect the expression of many other genes which is likely to be fatal

Question 15

What is apoptosis?

Answer 15

• process of programmed cell death (when cells in a multicellular organism deliberately destroy themselves)

Question 16

What is the process of apoptosis?

Answer 16

• cytoskeleton is hydrolysed by enzymes
• cell membrane forms blebs(small bulges)
• cell breaks up into membrane bound fragments which are removed by phagocytosis

Question 17

How is apoptosis regulated?

Answer 17

• homeobox genes control the rate of mitosis and apoptosis in different tissues, this controls the development of body plans
• If the event of a dna replication error, cells will trigger apoptosis to prevent mutations spreading
• starvation, break down muscles for respiration

Question 18

What are the uses for apoptosis?

Answer 18

• removing unnecessary body structures
• removing old cells
• apoptosis is essential in the development of body plans