Combined Biology - 4.6 Flashcards Preview

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Flashcards in Combined Biology - 4.6 Deck (80)
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1

What type of cell division leads to identical cells being formed?

Mitosis

2

What type of cell division leads to non-identical cells being formed?

Meiosis

3

What does sexual reproduction, in animals, involve?

The joining (fusing) of male and female gametes (sperm and egg)

4

What does sexual reproduction, in plants, involve?

The joining (fusing) of gametes (pollen and egg cells)

5

What does sexual reproduction lead to and why?

Variety in the offspring as there is mixing of genetic information

6

What is asexual reproduction?

One parent (no fusion or mixing of genetic information) leading to genetically identical offspring

7

What does meiosis do to the number of chromosomes in the gamete?

It halves it (46 to 23)

8

What happens to the number of chromosomes during fertilisation?

It doubles (male and female gametes both have 23 chromosomes, combining to make 46)

9

What key stages occur when a cell divides to form gametes (meiosis)?

1. Copies of the genetic information are made

2. The cell divides twice forming four gametes (each with a single set of chromosomes)

3. All the gametes are genetically different from each other

10

What is the genetic material in the nucleus of a cell composed of?

DNA

11

What is the structure of DNA?

A polymer made up of two strands forming a double helix

12

What is DNA contained in?

Chromosomes

13

What is a gene?

A small section of DNA on a chromosome

14

What does a gene code for?

A particular sequence of amino acids, which make specific proteins

15

What is the genome of an organism?

The entire genetic material of that organism

16

Why is having the human genome sequence important?

It will be of benefit to medicine

17

Why is understanding the human genome important?

• Genes linked to different types of disease can be searched for

• Inherited disorders can be understood / treated

• Migration patterns of the past can be traced

18

Explain the term: gamete

A sex cell (e.g. sperm or egg)

19

Explain the term: chromosome

A long molecule of DNA, found in the nucleus of a cell, which carries genes

20

Explain the term: gene

A short section of DNA, found on a chromosome, carrying the instructions needed to make a protein (and so controls the development of a characteristic)

21

Explain the term: allele

An alternative version of a gene

22

Explain the term: dominant

The allele for the characteristic that’s shown by an organism if two different alleles are present for that characteristic 

23

Explain the term: recessive

An allele whose characteristic only appears in an organism if there are two copies present

24

Explain the term: homozygous

Where an organism has two alleles for a particular gene that are the same

25

Explain the term: heterozygous

Where an organism has two alleles for a particular gene that are different

26

Explain the term: genotype

27

Explain the term: phenotype

The characteristics an organism has, e.g. tall

28

Give an example of characteristics controlled by a single gene

Fur colour in mice / red-green colour blindness in humans

29

What controls the phenotype (what is expressed)?

Alleles present (or genotype) operating at a molecular level to develop characteristics expressed (as a phenotype)

30

Which allele is always expressed?

The dominant (even if only one copy is present)