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Biology > Exam B6 > Flashcards

Exam B6 Flashcards

(64 cards)

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1
Q

DNA

A

double helix found in chromosomes.

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2
Q

Gene

A

small section of DNA that codes for a protein

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3
Q

Inheritance

A

Humans have 23 pairs of chromosomes.

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4
Q

Allele

A

different versions of the same gene.

One from mum, one from dad.

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5
Q

Dominant

A

always shows (B)

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6
Q

Recessive

A

only shows if both alleles are recessive (b)

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7
Q

Cystic fibrosis: caused by a

A

recessive allele

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8
Q

Polydactyly extra fingers caused by a

A

dominant allele

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9
Q

Genetic Diagrams (Punnett Squares)

A
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10
Q

Cystic fibrosis

A

recessive

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11
Q

Polydactyly extra fingers caused by a

A

dominant allele

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12
Q

Genetic Diagrams (Punnett Squares)

A
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13
Q

Fossils don’t form in

A

Soft tissue

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14
Q

GM crops can increase

A

yield and resist disease

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15
Q

What is Reproduction?

A

Reproduction is the process of making new organisms (offspring).

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16
Q

Asexual Reproduction

A

• Only 1 parent
• No fusion of gametes
• No variation – all offspring are genetically identical (clones)
• Happens by mitosis

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17
Q

Example of Asexual Reproduction

A

• Bacteria
• Strawberry runners
• Some fungi (like mould)

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18
Q

Sexual Reproduction

A

• 2 parents
• Involves fusion of male and female gametes (e.g. sperm + egg)
• Offspring show variation
• Uses meiosis to make gametes

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19
Q

What is the two types of Reproduction?

A

Asexual Reproduction
Sexual Reproduction

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20
Q

Gametes and Fertilisation

A

Flowers

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21
Q

What is Fertilisation

A

when the nuclei of two gametes join to form a zygote (fertilised egg)

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22
Q

Meiosis (Only in Sexual Reproduction)

A

• Makes gametes (sperm, egg, etc.)
• Chromosome number halves
• Introduces genetic variation

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23
Q

Steps of Fertilisation

A

Zygote → embryo → baby

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24
Q

Sexual Reproduction example

A

• Humans and animals
• Flowering plants (egg + pollen)

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25
Human cells:
• Normal cells = 46 chromosomes (23 pairs) • Gametes = 23 chromosomes
26
Advantages & Disadvantages Of asexual and sexual
27
Asexual reproduction =
no variation (clones)
28
Meiosis makes gametes with half….
half the chromosomes
29
Sexual reproduction =
variation due to mixing of genes
30
Dose Bacteria reproduce asexually or sexually
Bacteria reproduces asexually no sperm or egg involved
31
What is asexual reproduction?
Reproduction with one parent and no gametes; offspring are clones.
32
Fertilisation restores full number of chromosomes (back to 46 in humans)
Fertilisation restores full number of chromosomes (back to 46 in humans)
33
Advantages & Disadvantages Of asexual and sexual
34
What is sexual reproduction?
Reproduction involving two parents and the fusion of gametes.
35
What is fertilisation?
When the nuclei of a sperm and egg fuse to form a zygote
36
What is a gamete?
A sex cell (e.g. sperm, egg, pollen, ovule).
37
How many chromosomes in a human gamete?
23
38
What type of cell division makes gametes?
Meiosis
39
Name two organisms that reproduce asexually
Bacteria and fungi
40
What is Meiosis?
Meiosis is a type of cell division that: • Only happens in sexual reproduction • Produces gametes (sperm and egg cells) • Each gamete has half the number of chromosomes
41
Where does it happen? Meiosis
• In the testes (to make sperm) • In the ovaries (to make eggs) • In flowers (to make pollen and ovules)
42
Why is Meiosis important?
Meiosis: • Makes gametes • Each gamete has 23 chromosomes (instead of 46) • So that when fertilisation happens, the zygote ends up with 46 chromosomes
43
What is Gametes
haploid (half the DNA)
44
What is zygote
diploid (normal number)
45
What happens during meiosis?
1. A cell with 46 chromosomes copies its DNA. 2. Then it divides twice to make 4 gametes. 3. Each gamete: • Is genetically different • Has 23 chromosomes
46
Why does this cause variation?
Each gamete is genetically different — this causes genetic variation in offspring (a key advantage of sexual reproduction).
47
Difference Between Mitosis and Meiosis
48
Meiosis =
gametes made, not body cells
49
Gametes have….
23 chromosomes, not 46
50
Meiosis = 4 non or identical cells
4 non-identical cells ✅ Happens in testes and ovaries, not everywhere ✅ Leads to variation ✅ Meiosis = 2 divisions
51
What is meiosis used for?
Making gametes (sex cells)
52
How many divisions happen in meiosis?
Two
53
How many cells are made in meiosis?
4
54
Are the cells made by meiosis identical?
No — they are genetically different
55
Meiosis look like
56
Advantages & Disadvantages Of asexual and sexual
57
Dose gametes contain a single chromosome
Yes they do
58
In gametes are the chromosomes paired yes or no
They are not paired they single
59
Meiosis steps free siencelessons
1. All of the chromosomes are copied 2.the cell now divides into two 3.now both of the cells divide one more time forming the gametes In the gametes the chromosomes are now single not paired
60
Each gametes have different..
Alleles
61
Meiosis halves the number of…
Chromosomes and produces gametes
62
In sexual reproduction the gametes…
Join together Scientists call this fertilisation
63
In fertilisation the full number of chromosomes is….
Restored
64
What happened after fertilisation
Now the new cell divides by mitosis producing a clump of identical cells

Biology (28 decks)

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