Topic 1 - Genes And Enzymes

Question 1

What does a plant cell have that an animal cells doesn’t?

Answer 1

Rigid cell wall
Vacuole
Chloroplasts

Question 2

Nucleus?

Answer 2

Contains DNA that controls what the cell does.

Question 3

Cytoplasm?

Answer 3

Where the chemical reactions happen.

Question 4

Cell membrane?

Answer 4

Holds the cell together.

Controls what’s in and out.

Question 5

Mitochondria?

Answer 5

Reactions for respiration.

This releases energy that the cell needs to work.

Question 6

Rigid cell wall?

Answer 6

Made of cellulose, gives support for the cell.

Question 7

Vacuole?

Answer 7

Contains cell sap.

Question 8

Chloroplasts?

Answer 8

Where photosynthesis occurs. They contain chlorophyll.

Question 9

4 things that are in animal and plant cells?

Answer 9

Nucleus
Cytoplasm
Cell membrane
Mitochondria

Question 10

Features of a bacterial cell?

Answer 10

Chromosomal DNA
Plasmids
Flagellum
Cell wall

Question 11

Role of chromosomal DNA?

Answer 11

Controls the cells activities and replication. It floats free in the cytoplasm.

Question 12

Role of plasmids?

Answer 12

Small loops of extra DNA. Contain the gene for drug resistance.

Question 13

Flagellum role?

Answer 13

Rotates to make the bacterium move.

Question 14

Structure of DNA?

Answer 14

Two strands coiled together in a double helix. The two strands are held together by chemical bases. Adenine, cytosine, guanine, thymine.
Base pairing is A-T and C-G.

Question 15

What is a gene?

Answer 15

A section of DNA and the sequence of bases in a gene code for a specific protein.

Question 16

How did franklin and Wilkins work out the structure of DNA?

Answer 16

They found the helical structure by directing beams of x-rays onto crystallised DNA and looking at the patterns the x-rays formed as they bounced off.

Question 17

Watson and crick?

Answer 17

Made the model of the DNA molecule where all the pieces fitted together.

Question 18

Protein synthesis step one?

Answer 18

Transcription. The two DNA strands unzip. The coding strand of the DNA is copied. The DNA acts as a template to make mRNA (ribonucleic acid). This is like DNA but it is one strand made of C, G, A, and U (uracil).

Question 19

Protein synthesis step two?

Answer 19

Translation. mRNA moves out of the nucleus to the ribosome. The mRNA codes for the order of amino acids in the chain and is read. tRNA carries the amino acids that match the mRNA code to the ribosome. 3 bases (codon) are read at a time. The tRNA is an anticodon so matches to the mRNA codon. The ribosome links the amino acids in the order together to make a polypeptide. This folds into a special shape for the new protein to work.

Question 20

How are proteins made?

Answer 20

By organelles called ribosomes. DNA is found in the nucleus and can’t get out because it is really big. The cell needs to get the information from the DNA to the ribosome in the cell cytoplasm. This is done by using mRNA which is shorter than DNA but only a single strand. mRNA uses uracil instead of thymine. However uracil still joins to adenine. mRNA is like a messenger between the DNA in the nucleus and the ribosome.

Question 21

What is a mutation?

Answer 21

A change to an organisms DNA base sequence. This could affect the sequence of amino acids in the protein. This could affect the shape of the protein and it’s function. Mutations can be harmful, beneficial or neutral.

Question 22

How is a mutation harmful?

Answer 22

It can cause a genetic disorder, e.g cystic fibrosis.

Question 23

How is a mutation beneficial?

Answer 23

Produce a new characteristic that is beneficial to an organism. E.g. A mutation in genes on bacterial plasmids can make them resistant to antibiotics.

Question 24

What is neutral about mutations?

Answer 24

Not harmful or beneficial. They don’t affect a proteins function.

Question 25

What are enzymes?

Answer 25

Are catalysts produced by living things. Enzymes reduce the need for high temperatures. Speed up he useful chemical reactions in the body.

Question 26

What is a catalyst?

Answer 26

A substance which increases the speed of a reaction, without being changed or used up in the reaction.

Question 27

Examples of enzymes working inside and outside cells?

Answer 27

DNA replication - enzymes help copy a cells DNA before it divides by mitosis or meiosis. Protein synthesis - enzymes hold amino acids in place and form bonds between them. Digestion - enzymes are secreted into the gut to digest different food molecules.

Question 28

The lock and key mechanism?

Answer 28

Chemical reactions involve things being stuck together. The substrate is the molecule that is changed in the reaction. The active site joins onto it's substrate to catalyse the reaction. This only works with one substrate and enzymes have a high specificity for their substrate. The substrate must fit into the active site otherwise the reaction is not catalysed. This is the lock and key mechanism.

Question 29

Why don't enzymes work as well after 37 degrees?

Answer 29

Some of the bonds holding the enzyme together break. The enzyme losses it's shape and it's active site doesn't fit the shape of the substrate anymore. Therefore it can't catalyse the reaction.

Question 30

The human genome project?

Answer 30

Scientists tried to find all 25 000 genes curled up to form 23 chromosomes.

Question 31

Positives of the human genome project?

Answer 31

Predict and prevent diseases. Develop new and better medicines. Accurate diagnosis. Improve forensic science - DNA fingerprint.

Question 32

Negatives of the human genome project?

Answer 32

Increased stress - knowing they have bad genes. Gene-ism - people are under pressure not to have kids due to genes. Discrimination by employers and insurers - hard to get life insurance.

Question 33

What is genetic engineering?

Answer 33

The use of enzymes to cut and paste genes.

Question 34

How does genetic engineering work?

Answer 34

A useful gene is cut out from one organisms chromosome using restriction enzymes. The enzymes are then used to cut another organisms chromosome and then to insert the useful gene. This technique produces genetically modified organisms. E.g. Human genes can be used to make GM bacteria.

Question 35

Human benefits of genetic engineering?

Answer 35

Reducing vitamin A deficiency Producing human insulin Increasing crop yield

Question 36

Reducing vitamin A deficiency?

Answer 36

Beta-carotene is used by the body to make vitamin A. Vitamin A deficiency occurs in Asia and Africa. Golden rice is a variety of GM rice. It contains two genes from other organisms which together enable the rice to produce beta-carotene. Growing golden rice would be good in Asia and Africa.

Question 37

Producing human insulin?

Answer 37

The human insulin gene can be inserted into bacteria to produce human insulin quickly. It is also cheap.

Question 38

Increasing crop yield?

Answer 38

GM crops have their genes modified. E.g. Make them resistant to herbicides. Therefore increases crop yield.

Question 39

Controversy of genetic engineering?

Answer 39

GM crops affect the number of weeds. Reduces farmland biodiversity. GM crops might not be safe, people may develop allergies. Herbicide resistance may be picked up by weeds, forming a super weed.

Question 40

What is mitosis?

Answer 40

It makes new cells for growth and repair. Human body cells are diploid so they have two versions of each chromosome. When a cell divides it makes two genetically identical to the original cell. This is done to grow or replace cells that have been damaged.

Question 41

Mitosis step one?

Answer 41

In a cell that's not dividing the DNA is spread out in long strings. If the cell gets a signal to divide, it needs to duplicate it's DNA - so there's on copy of each new cell. The DNA is copied and forms X-shaped chromosomes. Each side of the chromosome is a duplicate to the other side.

Question 42

Mitosis step two?

Answer 42

The chromosomes then line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell. Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells.

Question 43

Mitosis step three?

Answer 43

Finally the cytoplasm divides. This forms two new diploid cells containing the exact dame DNA. Therefore they are genetically identical.

Question 44

What are gametes?

Answer 44

Meiosis involves gametes. Gametes only contain half the number of chromosomes for reproduction. Gametes are haploid because they contain only one copy of each chromosome. When two gametes combine in fertilisation they form a zygote which is diploid.

Question 45

What is meiosis?

Answer 45

Makes new cells that only contain half the original number of chromosomes. It only occurs in the reproductive organs. Meiosis is when a cell divides to from four haploid nuclei where the chromosomes are not identical.

Question 46

Meiosis step one - division 1?

Answer 46

Before the cell starts to divined it duplicates it's DNA. Each side of the chromosomes are an exact copy of each other. In the first division the chromosome pairs line up at the centre of the cell.

Question 47

Meiosis step two - division 1?

Answer 47

They're then pulled apart, so each new cell only has a copy