B13.1 - 13.5 - Reproduction + DNA (set A)✔️

Question 1

Define sexual reproduction?

Answer 1

Where genetic information from two organisms (father + mother) is combined to produce offspring which are genetically different to either parent

Question 2

What do both parents produce for sexual reproduction and by which process?

Answer 2

Mother and father produce gametes by meiosis eg sperm and egg cells in animials

Question 3

How many chromosomes does each gamete contain in humans?

Answer 3

23 chromosomes - which is half the number of chromosomes in a normal cell (as a gamete only has 1 of each chromosome instead of 2)

Question 4

what happens when the egg is fertilised by the sperm cell?

Answer 4

The egg and sperm cell fuse together (fertilisation) to from a cell with the full number of chromosomes (half from the mother and half from the father)

Question 5

What is required for sexual reproduction?

Answer 5

Involves the fusion of male and female gametes - so requires 2 parents

Question 6

What causes variation in offspring?

Answer 6

The mixture of genetic information as the offspring receives a miture of chromosomes from both parents which code for different things eg hair colour

Question 7

Define asexual reproduction?

Answer 7

Involves only 1 parent so the offspring are genetically identical to the parent and happens by mitosis - there is no fusion of gametes and no mixing of chromosomes and no genetic variation

Question 8

Significance of asexual reproduction happening by mitosis?

Answer 8

Cells divide in two with the new cell having exactly the same genetic information as the parent cell so it is called a clone

Question 9

Example of some thngs which reproduce asexualy?

Answer 9

Bacteria , some plants and some animials

Question 10

Explain step 1 of meiosis?

Answer 10

First, cell duplicates its genetic information forming two armed chromosomes - one arm of each chromosome is the exact copy of the other arm - after replication chromosomes arrange themselves in pairs

Question 11

Explain step 2 of meiosis?

Answer 11

In the first divison in meiosis the chromosomes pair line up in the centre of the cell

Question 12

Explain step 3 of meiosis?

Answer 12

Pairs are then pulled apart (so each new cells only has one copy of each chromosome) both the mothers and fathers chromosomes go into each new cell

Question 13

Explain step 4 of meiosis?

Answer 13

In the second division the chromosomes line up again - in the centre of the cell the arms of the chromosomes are pulled apart

Question 14

Explain step 5 of meiosis?

Answer 14

You get 4 gametes which only has a single set of chromsomes in it - each gamete is genetically different from the others because they get shuffled up during meiosis and each gamete only gets half of them at random

Question 15

What is the only location where meiosis takes place in humans?

Answer 15

Only happens in the reproductive organs to make gametes (sex cells)

Question 16

What happens after the gametes have fused during fertilisation?

Answer 16

Resulting new cell divides by mitosis to make a copy of itself which continues to form lots of new cells in an embryo - as the embryo starts to develop these cells start to differentiate into different types of specialised cells that make up a whole organism

Question 17

Advantages of sexual reproduction over asexual?

Answer 17

-variation in offspring
-variation increases chance of a species survival in changing enviorments
-natural selection
-selective breeding - produce indivisual with desirable characteristics

Question 18

Define natural selection?

Answer 18

Better indivisuals with characteritstics that make them better adapted to the enviorment have a better chance of survival and will pass these characteristics on

Question 19

Advantages of asexual reproduction over sexual?

Answer 19

-only needs to be 1 parent
-uses less energy - organisms dont have to find a mate
-faster then sexual reproduction
-many identical offspring can be produced in favourable conditions

Question 20

Example of an organism which can produce both sexualy and asexually?

Answer 20

-malaria - reproduces sexually when carried by mosquito and asexually when in human host
-species of fungus - reproduce asexualy by spores but also sexually to give variation
-species of plants - produce seeds sexually but also reproduce asexually

Question 21

What are chromosomes made up of?

Answer 21

Long molecules of a chemical known as deoxyribonucleic acid (DNA) - DNA is a long polymer made up of many repeating units, these very long strands of DNA twist and spiral to form a double helix structure

Question 22

What are genes? what do they code for?

Answer 22

Small section of DNA on a chromosome, and is where the genetic information is sored - each gene codes for a particular sequence of amino acids to make a specific protein (these proteins include enzymes aswell)

Question 23

What is the genome of an organism?

Answer 23

Is the entire genetic material of the organism - include all of the chromosomes and the genetic material found in the mitchondria (mitochondria contain their own DNA which you inherit from your mother becasue it come from mitchondria in the egg)

Question 24

Why is understanding the human genome important?

Answer 24

Helps us understand inherited disorders such as cystic fibrosis and sickle cell disease and overcoming them through medecine or repairing faulty genes

Question 25

What is a nucleotide?

Answer 25

The combination of a sugar, a phosphate and a base (A,C,G,T) - it is these repeating nucleotide units which make up the DNA polymer

Question 26

What are the long strands of DNA made up of?

Answer 26

Alternating sugar and phosphate sections which make up the backbone of the molecule. attached to each sugar is one of the four different compounds called bases represented with the letters A,C,G and T

Question 27

What are Bases in regard to DNA?

Answer 27

Attached to each sugar is one of four different compounds which are called bases they are represented by the letters A,C,G,T

Question 28

How are nucleotides arranged? Explain importance of the order in which the three bases are aranged?

Answer 28

Nucleotide units are grouped into threes, and each group of three bases code for a particular amino acid which make a specific protein (order of bases controls order in which amino acids are assembled). A change in a single group of bases can be enough to change or distrupt the whole protein structure

Question 29

Describe fully step 1 to 3 of how a protein synthesis takes place?

Answer 29

1)template leaves the nucleus and binds to surface of a ribosome

2)the cytoplasm contains carrier molecules each attached to a specific amino acid - the carrier molecules attach themselves to the template in the order given by the DNA

3)the amino acids are joined together to form a specific protein

Question 30

Describe fully steps 4 to 5 of how a protein synthesis takes place?

Answer 30

4)carrier molecules keep bringing specific amino acis to add to the growing protein chain in the correct order until the template is completed

5)the protein detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm to pick up more amino acids

Question 31

Describe what happens once the protein chain is completed?

Answer 31

The molecules and the carrier molecule folds up to form a unique shape that will enable it to carry out its functions in the cell eg if it is going be an enzyme it will fold to produce the active site

Question 32

How does the template leave the nucleus when making proteins?

Answer 32

Template it is small enough to leave the nucleus through the pores in the nuclear membrane

Question 33

What are the 4 complementary base pairings for DNA? Which bases go together?

Answer 33

A - T
T - A
(A always has to pair with T)

C - G
G - C
(C always has to pair with G)

Question 34

What do long strands of DNA consit of?

Answer 34

Consit of alternating sugar and phosphate sections - attached to each sugar is one of the four bases - DNA is a polymer made up of repeating nucleotide units

Question 35

Significance of the order of the nuceleotides three bases?

Answer 35

The order of the bases controls the order in which the amino acids are assembled to produce a particular protein - a change or mutation in a single group of bases can be enough to distrup the whole protein structure

Question 36

Explain what happens when the protein chain is complete?

Answer 36

The completed chain folds up to form a unique shape - enables the proteins to do their job as enzymes, hormones or forming structures in the body

Question 37

How is the template for a protein produced?

Answer 37

Genes in the DNA produce a template for the protein - the template reflects the sequence of bases in the DNA