dna and inheritance - biology revison

Question 1

what is found inside nearly all cells?

Answer 1

a nucleus

Question 2

what does the nucleus contain?

Answer 2

chromosomes

Question 3

what are chromosomes made out of?

Answer 3

dna- deoxyribonucleic acid

Question 4

what is the genome?

Answer 4

the entire genetic code of an organism

Question 5

there are four different nucleotides each with four different bases called..

Answer 5

adenine
thymine
cytosine
guanine

Question 6

what are dna strands made out of?

Answer 6

polymers (large molecules) made up of monomers (smaller subunits) called nucleotides

Question 7

what is the structure of a nucleotide?

Answer 7

a nucleotide is made up of a phosphate group, sugar and a base

thee sugar and phosphate molecules alternate, with paired chemicals between each strand called bases

Question 8

what is a nucleotide known as?

Answer 8

the backbone of dna

Question 9

what bases pair up with eachother?

Answer 9

thymine + adenine
guanine + cytosine
this is called complementary base pairing

Question 10

how do you extract dna from fruits?

Answer 10

1. put strawberries in a bag and crush to a pulp by hand (this breaks apart the cell walls and removes the insoluble part)
2. put in 5cm³ of dish soap and 2 heaped spoons of salt into the bag (the dish soap breaks down the membranes of the cell and the nucleus)
3. mix it all up
4. after 15 minutes, put the bag into a plastic beaker with ice, and on top of the bag
5. put a cloth over the beaker with an elastic bag (protease is sometimes added to break down protein and destroy any enzymes that could break down the dna)
6. push down the middle of the j cloth to make a hollow
7. then, put the mixture into the hollow so it can filter
8. then take the cloth off and put it in the bin

9.rhen put the filtrate into a cooled test tube, then out the ice cold ethanol into the tube ( cold ethanol helps the dna to precipitate)

10. then use a wire to lift out the white stringy layer - dna

Question 11

facts about the nucleus

Answer 11

• it contains 46 chromosomes
  -it holds and protects dna
  -the cell membrane protects the nucleus

Question 12

facts about the chromosomes

Answer 12

-a gene is a section of a chromosome
-a long strand of chromosomes is called a long coil of dna
-chromosomes are made of dna

Question 13

facts about dna

Answer 13

• it has a double helix structure
• bonded together with weak hydrogen bonds
• joined together by pairs of bases? base pairs
• dna carries code up of base pairs

Question 14

what is variation?

Answer 14

the difference between organisms of the same species

Question 15

what are species?

Answer 15

organisms that can breed together to produce fertile offspring

Question 16

what is variation caused by?

Answer 16

• genes (inherited from parents in chromosomes)
• the environment
• both genes and the environment

Question 17

what is a phenotype?

Answer 17

a characteristic that we can see or measure

Question 18

what is an acquired characteristic?

Answer 18

something caused by the environment

Question 19

what can genetic variation be caused by?

Answer 19

• mutations (a random change in genes or chromosomes)
• sexual reproduction

Question 21

what is darwin’s theory of natural selection?

Answer 21

variation
l
mutation ( a random change in a gene)
l
characteristics most suited to the environment (alleles that are responsible for the useful characteristic to be passed on to the next gen)
l
survive (survival of the fittest)
l
reproduce
l
genes passed on to the next generation
l
mutant genes become more common in the population (over a long period of time)

Question 22

what is a genotype?

Answer 22

the two alleles of a gene that an organism has

Question 23

what does homozygous recessive mean?

Answer 23

when the genotype has two lowercase letters

Question 24

what does homozygous dominant mean?

Answer 24

when the genotype has two uppercase letters

Question 25

what does heterozygous mean?

Answer 25

when the genotype has one uppercase and one lowercase letter

Question 26

what is a genetic cross / punnett square?

Answer 26

it is used to find out what genes someone is going to get
- punnett squares should ALWAYS be labelled with phenotypes

Question 27

what is a zygote?

Answer 27

the fertilised egg cell

Question 28

what is the human genome project?

Answer 28

from 1990 to 2003, people mapped the location of 21000 human genes, and they found that 1800 were linked to diseases. the project was done to help let people know what diseases they could have from their genes.

• the genome is the entire genetic makeup of an individual
• the problems of possibly knowing what diseases you could have, is that you could stress a lot, have pressure to not have children, or discrimination by employers and life insurance companies
• it could help by knowing possible diseases because you can predict and prevent
• you could also test and treat, and have genetic screening/ have medicines
• you could also have better medicines