6.1.1 Cellular control

Question 1

What causes cells with the same DNA to have different structures and functions?

Answer 1

The activation and deactivation of different genes leading to production of different proteins, causing cells to specialise

Question 2

What happens to genes in a specialised cell?

Answer 2

Some genes are activated (expressed) and transcribed into mRNA, while others are inactivated. Only activated genes lead to protein production.

Question 3

How do proteins influence cell specialisation?

Answer 3

modify the cell by changing its structure and controlling cellular processes

Question 4

What happens during the differentiation of a stem cell into a red blood cell, for example?

Answer 4

genes responsible for haemoglobin production are activated
proteins that will destry the nucleus are activated
other genes will be inactivated

Question 5

What are transcription factors (TFs)?

Answer 5

Proteins that control gene activation and deactivation by influencing transcription.

Question 6

What are the two types of transcription factors?

Answer 6

-Activator
-Repressor

Question 7

how do Activators function in gene expression

Answer 7

help RNA polymerase bind to the promoter region, activating gene transcription.

Question 8

how do repressors inhibit gene expression

Answer 8

bind to the gene and block RNA polymerase from attaching, preventing transcription.

Question 9

What is an operon?

Answer 9

A section of DNA in prokaryotes that contains a cluster of genes controlled by a single promoter.

Question 10

What are the three main components of an operon?

Answer 10

-structural genes (lacZ, lacY, lacA)
-control elements
-regulatory gene

Question 11

What do structural genes in an operon do?

Answer 11

code for useful proteins, such as enzymes

Question 12

What is the role of control elements in an operon?

Answer 12

Promoter – A DNA sequence where RNA polymerase binds to start transcription.
Operator – A DNA sequence where transcription factors (activators or repressors) bind to regulate gene expression.

Question 13

What does the regulatory gene in an operon do?

Answer 13

codes for transcription factors (activators and repressors)

Question 14

What is the lac operon?

Answer 14

A section of DNA found in some bacteria that controls the production of enzymes needed to digest lactose when glucose is unavailable.

Question 15

What happens when lactose is absent?

Answer 15

1. The regulatory gene (lacI) produces the lac repressor.
2. The lac repressor binds to the operator, blocking RNA polymerase from binding to the promoter.
3. The structural genes (lacZ, lacY, lacA) are not transcribed, so no lactose-digesting enzymes are made.

Question 16

What happens when lactose is present (and glucose is not)?

Answer 16

1. Lactose binds to the lac repressor, causing a shape change.
2. The repressor can no longer bind to the operator, so RNA polymerase can bind to the promoter.
3. The structural genes (lacZ, lacY, lacA) are transcribed, producing enzymes to digest lactose.

Question 17

What do the structural genes in the lac operon code for?

Answer 17

-lacZ=β-galactosidase
-lacY=lacotse permease
-lacA=lactose acetylase

Question 18

what is the function of β-galactosidase?

Answer 18

breaks down lactose into glucose & galactose

Question 19

what is the function of lactose permease?

Answer 19

membrane protein that transports lactose into the cell

Question 20

What is the genome?

Answer 20

the complete set of genes present in a cell or organism

Question 21

What is splicing?

Answer 21

A post-transcriptional process in eukaryotic cells where introns (non-coding regions) are removed from mRNA before translation.

Question 22

Why is splicing necessary?

Answer 22

Introns do not code for amino acids, so they must be removed to produce mature mRNA that can be translated into a functional protein.

Question 23

What are introns and exons?

Answer 23

Introns=Non-coding regions of DNA that are removed during splicing
Exons=Coding regions that remain in the mRNA and are translated into proteins

Question 24

What is post-translational control?

Answer 24

The regulation of protein activity after translation, often by modifying their structure to activate them.

Question 25

Why are some proteins synthesised in an inactive form

Answer 25

To prevent premature activity and ensure they are only activated when needed.

Question 26

How does cAMP activate proteins?

Answer 26

Acts as a second messenger and binds to proteins, causing a conformational change that alters their 3D sctructure and activity.

Question 27

what is cyclic AMP formed by?

Answer 27

the enzyme adenyl cyclase

Question 28

name a protein that is activated by cAMP and what does it do once activated

Answer 28

protein kinase A (PKA) can activate other proteins

Question 29

What is the body plan?

Answer 29

the general organisation of an organism's body, e.g. the head at the top and feet at the bottom

Question 30

What are Hox genes?

Answer 30

A group of genes that control the arrangement of body parts by regulating gene expression during development.

Question 31

Why are Hox genes considered highly conserved?

Answer 31

Their DNA sequences have remained nearly unchanged through evolution due to their crucial role in body development.

Question 32

What happens if a mutation occurs in a Hox gene?

Answer 32

can cause severe developmental defects, unlikely to be passed on

Question 33

How do Hox genes control body plan development?

Answer 33

they are transcribed into hox proteins that act as transcription factors, switching certain genes on or off

Question 34

What is the homeodomain?

Answer 34

A special region in Hox proteins that binds to DNA, allowing them to regulate gene expression.

Question 35

How do Hox proteins influence cell differentiation?

Answer 35

In different body regions, Hox proteins activate genes needed for specific structures (e.g., toes, hair follicles) and repress genes for unrelated structures (e.g., eyes in feet cells).

Question 36

What is the role of mitosis in the development of the body plan?

Answer 36

to create the bulk of the body parts, generating enough cells to fill the body

Question 37

what is apoptosis

Answer 37

the process of controlled cell death

Question 38

What is the role of apoptosis in the development of the body plan?

Answer 38

'chisels away' excess cells, to form structures such as fingers and toes

Question 39

describe the process of apoptosis

Answer 39

1. Enzymes are acctivated that break down cell components (e.g. DNA and proteins). 2. The cell shrinks and fragments. 3. The cellular debris is engulfed and removed by macrophages.

Question 40

What triggers apoptosis?

Answer 40

-Internal stimuli (such as DNA damage) -External stimuli (like pathogenic infection).

Question 41

How do genes regulate mitosis and apoptosis in different cells?

Answer 41

-In some cells, genes that control mitosis are activated, while genes controlling apoptosis are switched off. -In other cells, this is reversed.

Question 42

What is a mutation?

Answer 42

any change to the base sequence

Question 43

What is a substitution mutation?

Answer 43

one base is replaced for another resultng in either a change to a single amino acids or no change at all (genetic code is degenerate)

Question 44

what is an insertion mutation?

Answer 44

one or more base is added it will change the codon and all subsequent codons

Question 45

what is a deletion mutation?

Answer 45

one or more bases is removed it will change the codon and all follwing codons

Question 46

what is an inversion mutation?

Answer 46

a sequence of bases is reversed resulting in a change to a single amino acid

Question 47

which mutations are frameshift?

Answer 47

insertion deletion

Question 48

How can a mutation have a neutral effect on a protein's function?

Answer 48

1. The mutation changes a base in a triplet, but the amino acid coded for remains the same (genetic code is degenerate). 2. The mutation produces a chemically similar amino acid that functions like the original one. 3. The mutated amino acid is located far from the protein's active site, so the protein still functions normally.

Question 49

What effect does the mutation have on the protein?

Answer 49

alterted tertiary structure

Question 50

Can mutations ever be beneficial?

Answer 50

Yes - antibiotic resistance in bacteria