Reproduction, the genome and gene expression

Question 1

what are the advantages of sexual reproduction? (3)

Answer 1

-produces variation in the off springs
-survival advantage: species can adapt to new environments due to variation
-a disease is less likely to affect all population

Question 2

what are the disadvantages of sexual reproduction? (2)

Answer 2

-time and energy needed to find a mate
-not possible for isolated individual (e.g species on the brink of extinction)

Question 3

advantages of asexual reproduction: (3)

Answer 3

-population can increase rapidly if the (environmental) conditions are favourable
-only one parent is needed so it’s more time and energy efficient than sexual rep
-faster than sexual reproduction

Question 4

disadvantages of asexual reproduction: (3)

Answer 4

-no variation in population
-specie may be suited to only one habitat
-disease may affect entire population

Question 5

what does meiosis produce? and what does this result in?

Answer 5

four daughter cells, each with half the number of chromosomes
genetically different haploid gametes

Question 6

what does meiosis produce in animals and plants?

Answer 6

sperms and egg cells in animals and pollen in plants

Question 7

what is the genetic material in the nucleus of a cell made up of?

Answer 7

DNA

Question 8

what is DNA made up of?

Answer 8

a polymer made up of nucleotides

Question 9

what are nucleotides made up of?

Answer 9

a sugar and a phosphate group, with one of four different bases, A, C, T or G, attached

Question 10

how is the double-helix structure of DNA formed?
and what holds this double-helix structure?

Answer 10

The nucleotides join together, forming two strands.
-weak hydrogen bonding between complementary base pairs

Question 11

what are the complementary base pairs?

Answer 11

thymine pairs with adenine (T–A)
guanine pairs with cytosine (G–C).

Question 12

Describe the structure of DNA:

Answer 12

-a polymer made up of two strands coiled to form a double helix
-strands are linked by a series of complementary base pairs joined together by weak hydrogen bonds
-nucleotides that consist of a sugar and phosphate group with one of the four different bases attached to the sugar

Question 13

what are chromosomes?

Answer 13

long strands of DNA, made up of genes

Question 14

what is a gene?

Answer 14

a small section of DNA in a chromosome

Question 15

what does a gene do?

Answer 15

Each gene codes for a particular sequence of amino acids in order to make a specific protein

Question 16

what is a genome?

Answer 16

the entire DNA of an organism

Question 17

how is the HGP helpful in medicine?

Answer 17

-mapping of a person’s genome can help in predicting how likely they are to develop certain conditions

Question 18

Method for extracting DNA from a kiwi: (5)

Answer 18

1- Peel the skin from half a kiwi fruit and mash it up
2- Mix a teaspoon of salt and small volume of washing up liquid into the fruit
3- Gently heat this mixture at about 60°C for five minutes
4- Filter the mixture and retain only the filtrate (the filtered liquid)
5- Cool using an ice bath and gently pour chilled ethanol onto the top of the filtrate

Question 19

what will you observe from the fruit DNA extraction ?

Answer 19

strands of DNA with bubbles in them at the boundary between the filtrate and the chilled ethanol.

Question 20

what are the four bases?

Answer 20

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

Question 21

what does the sequence of bases in the gene control?

Answer 21

which amino acids are joined in order to make a specific new protein (or enzyme) molecule

Question 22

what happens to amino acids after they have joined together?

due to this, how could you define a protein?

Answer 22

they are folded into their correct shape to make them functional.

A protein is a chain of amino acids, folded into the correct shape.

Question 23

what is a triplet?

what is its purpose?

Answer 23

three bases.

A triplet of DNA bases codes for one amino acid.

Question 24

describe the process of genes coding for proteins: (3)

Answer 24

1- Each triplet of bases codes for one particular amino acid.
2- Amino acids are made in the number and order dictated by the number and order of base triplets.
3- The amino acid molecules join together in a long chain to make a protein molecule. The number and sequence of amino acids determines which protein is produced.

Question 25

what needs to happen in order for a gene to be expressed?

where does this process take place?

Answer 25

the base sequence of DNA is copied or transcribed into mRNA

the nucleus

Question 26

what must happen to the strands of DNA before the transcription process?

how does this occur?

Answer 26

The two strands of the DNA helix are unzipped

by breaking of the weak Hydrogen bonds between base pairs.

Question 27

what causes the unwinding of the two DNA strands?

Answer 27

This unwinding of the helix is caused by an enzyme (helicase enzyme).

Question 28

what does a single codon code for?

Answer 28

a single amino acid

Question 29

describe the process of transcription into the mRNA: (4)

Answer 29

1- The two strands of the DNA helix are unzipped by breaking of the weak Hydrogen bonds between base pairs. This unwinding of the helix is caused by an enzyme (helicase enzyme).
2- The enzyme RNA polymerase attaches to the DNA in a non-coding region just before the gene.
3- RNA polymerase moves along the DNA strand. Free RNA nucleotides form hydrogen bonds with the exposed DNA strand nucleotides by complementary base pairing to form a strand of mRNA
4- The newly formed strand of mRNA is now ready to leave the nucleus and travel to the ribosome.

Question 30

what is the difference between the bases of DNA and RNA?

Answer 30

RNA nucleotides contain the same bases as DNA, except that T is replaced by U. U base pairs with A.

Question 31

what is the relationship between the the strand of mRNA and the DNA?
-what is this called?

Answer 31

the mRNA will be an exact opposite copy of the DNA strand

a complementary copy