[Part 2]- B12- reproduction 🧬

Question 1

What’s mitosis ?

Answer 1

• mitosis, is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA, produced by the parent cell during DNA replication

Question 2

RECAP: Describe the stages of the cell cycle [4]

Hint: growth of sub-cellular structures and…

Answer 2

• cell grows, and the number of sub-cellular structures [such as ribosomes and mitochondria] are increased.
• DNA then replicates to form two copies of each chromosomes
• In mitosis, one set of chromosomes is pulled to each end of the cell. The nucleus then divides
• the cytoplasm and cell membrane divides, to form two identical (daughter) cells

Question 3

What’s meiosis ?

Answer 3

• meiosis, is a type of cell division that gives rise to four reproductive cells [gametes], each with half the chromosome number of the parent cell.

Question 4

Where does meiosis take place ?

Answer 4

• meiosis only takes place in the reproductive organs.
• with humans this is the testes in males, and the ovaries in females

Question 5

What’s the process of meiosis ?

Answer 5

• firstly, all of the chromosomes are copied and the cell now divides into two.
• and these two cells, now divide one more time to form gametes

Question 6

What does meiosis do ?

Answer 6

• meiosis, halves the number of chromosomes.
• ; meiosis also produces four gametes from one original cell, that are all genetically different from each other

Question 7

• Fill in the gaps: each gamete has _________ alleles

Answer 7

• each gamete has different alleles

Question 8

What happens to gametes during fertilisation ?

Answer 8

• during fertilisation, gametes join together so the cell now has a normal number of chromosomes
• this means, fertilisation restores the full number of chromosomes

Question 9

What’s the difference between meiosis 🆚 mitosis ?

Answer 9

• meiosis, is a type of cell division that gives rise to four reproductive cells [gametes], each with half the chromosome number of the parent cell.
• ; mitosis, is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA, produced by the parent cell during DNA replication

Question 10

What happens to a cell after fertilisation ?

Answer 10

• after fertilisation, the cell divides by mitosis to produce a clump of identical cells [known as an embryo]

Question 11

RECAP: What are the three functions of mitosis ?

Answer 11

• [mitosis is essential for] growth and development of multicellular organisms [e.g- plants and animals]
• mitosis takes place, when an organism repairs itself [e.g- when a broken bone heals]
• mitosis also happens during asexual reproduction

Question 12

Where is DNA found ?

Answer 12

• DNA is contained in structures known as chromosomes, which is then found in the nucleus of cells.

Question 13

What does DNA consist of ?

Answer 13

• DNA, consists of two strands and each strand is a polymer.
• this means, each strand is made by joining together lots of smaller molecules

Question 14

What is a double-helix ?

Answer 14

• a double-helix, is a term used to describe the physical structure of DNA, which involves two strands of nucleotides twisted around each other to form a shape [known as the double-helix]

Question 15

Define the term ‘gene’

Answer 15

• a gene, is a small section of DNA on a chromosome [that codes for a particular sequence of amino acids, to make a specific protein]

Question 16

Give an example, of how genes code a specific sequence of amino acids ?

Answer 16

• the blood type gene [chromosome number 9], codes sequence of amino aids for the protein that determines blood type.
• this is because, proteins are made by joining together amino acids

Question 17

How are chromosomes in pairs ?

Answer 17

• chromosomes are found in all body cells, except for gametes.
• these pair of chromosomes, are known as homologous pairs and have exactly the same genes, in the same location on the chromosome.
• this is because they’re inherited from each parent therefore, one member of each homologous pair will each come from the mother and the father

Question 18

What is the genome ?

Answer 18

• the genome, is the entire genetic material of an organism
• [the human genome, is the entire genetic material that makes a human]

Question 19

What’s the difference between a gene 🆚 a genome ?

Answer 19

• a gene, is a small section of DNA on a chromosome [that codes for a particular sequence of amino acids, to make a specific protein]
• ; the genome, is the entire genetic material of an organism

Question 20

Why is it important, that scientists have now studied the entire human genome ?

Answer 20

• understanding the human genome, helps us to search for genes that are linked to a disease [e.g- genes that increase the risk of developing a cancer, or alhezimers disease]

Question 21

What’s a second reason, why it’s important, to understand the entire human genome?

Answer 21

• understanding the human genome, helps us to understand and treat inherited disorders such as cystic fibrosis.

Question 22

What’s a third reason, why it’s important, to understand the entire human genome?

Answer 22

• the human genome, allows us to trace human migration patterns from the past- therefore, this can help people to discover their ancestry

Question 23

What are homologous pairs of chromosomes ?

Answer 23

• homologous pairs of chromosomes:
• carry the same genes in the same position, and are the same shape; they don’t necessarily carry the same alleles
  [form] of each gene

Question 24

Why don’t homologous pairs of chromosomes, carry the same alleles ?

Answer 24

• the genes on these chromosomes may have been mutated as they passed down for generations, forming new alleles.
• these alleles typically perform the same function, such as determining eye color; they may have different outcomes due to the mutations they possess.