B1.2 - What happens in cells - DNA

Question 1

where is DNA found?

Answer 1

in nucleus of all cells

Question 2

what are chromosomes?

Answer 2

long DNA molecules are coiled up in chromosomes

Question 3

how many chromosomes do each human body cell have?

Answer 3

46 chromosomes in 23 pairs

Question 4

what are genes made up of?

Answer 4

DNA

Question 5

what is DNA?

Answer 5

Deoxyribonucleic acid is a polymer made of 4 different nucleotides

Question 6

what do the nucleotides in DNA consist of?

Answer 6

a sugar molecule, phosphate group and 1 of 4 different bases (A, T, G, C)

Question 7

DNA bases names

Answer 7

A - adenine
T - thymine
G - guanine
C - cytosine

Question 8

which DNA bases go together?

Answer 8

A and T

G and C

Question 9

what do DNA molecules carry?

Answer 9

they carry the code for making proteins

Question 10

what is the definition of a gene?

Answer 10

the section of DNA that codes for a particular protein

Question 11

what is transcription?

Answer 11

• as DNA code remains in nucleus, a copy of a short section is made in the form of a molecule called mRNA (messenger RNA)
• mRNA copies the code from one side of the DNA molecule called the template strand - if there’s a C on DNA then the mRNA will match up adding a G to the code

Question 12

where does mRNA travel to and from

Answer 12

from the nucleus to the ribosomes where translation occurs

Question 13

in an RNA nucleotide what is base A paired with?

Answer 13

U

Question 14

what is translation?

Answer 14

• proteins are long chains of amino acids
• at ribosome the code on the mRNA is used to join amino acids in a specific order to make a protein
• a triplet code - 3 bases on the mRNA codes for a specific amino acid - e.g CGU codes for a diff amino acid to ACG

Question 15

what is translation?

Answer 15

• proteins are long chains of amino acids
• at the ribosome, the code on the mRNA is used to join amino acids in a specific order to make a protein
• a triplet code - 3 bases on the mRNA codes for a specific amino acid

Question 16

what different amino acid does CGU code for?

Answer 16

GCA

Question 17

Making proteins

Answer 17

• the DNA code stays in the nucleus
• it’s copied onto a messenger molecule (mRNA)
• code is carried into cytoplasm by mRNA
• the mRNA attaches to a ribosome
• ribosome ‘reads’ code and assembles amino acids in the correct order to make a protein

Question 18

what is mitosis?

Answer 18

the process by which body cells divide & produces 2 genetically identical daughter cells - clones

• 1 set of chromosomes goes into each new daughter cell - allows growth, repair of damaged tissue & replacement of cells
• also happens during asexual reproduction

Question 19

4 stages of cell cycle

Answer 19

1. DNA replication
2. movement of chromosomes - mitosis
3. cell splitting - cytokinesis
4. growth of daughter cell

Question 20

stage 1 of cell cycle - DNA replication

Answer 20

• DNA molecule unzips forming 2 separate strands
• bases are exposed
• free DNA nucleotides pair up with their complimentary bases
• new backbones form, producing 2 identical DNA molecules (chromosomes)

Question 21

stage 2 of cell cycle - mitosis

Answer 21

• chromosomes line up across centre of cell
• exact copies separate & move to opposite ends of cell
• 2 new nuclei form containing full set of identical chromosomes

Question 22

stages 3 & 4 of cell cycle - cytokinesis and growth

Answer 22

• cell membrane pinches in, enclosing the new nuclei
• the OG cell splits in 2, producing 2 genetically identical daughter cells - cytokinesis
• each daughter cell will then grow & cycle will begin again

Question 23

stem cells

Answer 23

• unspecialised cells
• have ability to divide by mitosis
• found in human embryos and some adult cells (e.g. bone marrow, umbilical cord blood and the placenta - and meristem in plants)