Reproduction and Inheritance Flashcards
1
Q
What are human body cells?
A
diploid
2
Q
What does diploid mean?
A
The cells have two copies of each chromosome, arranged in pairs
3
Q
How many chromosomes does a human cell nucleus contain?
A
46
4
Q
What is the diploid number for a human?
A
46
5
Q
What is DNA
A
A list of instructions on how to put an organism together and make it work
6
Q
What is each separate gene in a DNA molecule?
A
A chemical instruction that codes for (says how to make) a particular protein
7
Q
Why are proteins important?
A
They control most processes in the body and determine inherited characteristics
8
Q
What are alleles?
A
Different versions of the same gene
9
Q
What structure is DNA?
A
A double helix
10
Q
What are the two strands in DNA held together by?
A
chemicals called bases
11
Q
What are the four different bases?
A
Adenine
Cytosine
Guanine
Thymine
12
Q
What is the pairing of the bases? And what is it called?
A
A-T and C-G
complimentary base-pairing
13
Q
DNA is a type of…
A
nucleic acid
14
Q
What hold the pairs of bases together?
A
hydrogen bonds
15
Q
A sequence of three bases codes for…
A
an amino acid
16
Q
What are the two types of cell division?
A
meiosis and mitosis
17
Q
When does mitosis occur?
A
in asexual reproduction and growth and repair
18
Q
What are the end products of mitosis?
A
Two cells containing exactly the same DNA (genetically identical)
19
Q
What is mitosis?
A
When a cell reproduces itself by splitting to form two cells with an identical set of chromosomes
20
Q
What does meiosis produce?
A
Four haploid cells whose chromosomes are NOT identical
21
Q
Sexual reproduction involves…
A
the fusion of male and female gametes
22
Q
What are gametes?
A
sperm cells and egg cells
23
Q
What are gametes like in comparison with normal cells in terms of their chromosomes?
A
haploid - they have half the number of chromosomes in a normal cell
24
Q
In humans, each gamete contains how many chromosomes?
A
23
25
What is another name for a fertilised egg?
A zygote
26
What does a zygote develop into
an embryo
27
Is the fertilisation of gametes random? and what does this produce?
YES, this produces genetic variation in the offspring
28
What is the male reproductive part of a flower called?
The stamen
29
What is the female reproductive part of a flower called?
The carpel
30
What does the stamen consist of?
The anther
| The filament
31
What does the anther contain?
pollen grains - these produce the male gametes (sperm)
32
What is the filament?
The stalk that supports the anther
33
What does the carpel consist of?
Stigma
style
ovary
34
What is the stigma?
the end bit that pollen grains attach to
35
What is the style?
The section that supports the stigma
36
What does the ovary contain?
the female gametes (eggs)
37
What is pollination?
The transfer of pollen from an anther to a stigma, so that the male gametes can fertilise the female gametes in sexual reproduction
38
What is cross-pollination?
A type of sexual reproduction where pollen is transferred form the anther of one plant to the stigma of another
39
What do plants that cross-pollinate rely on?
insects and wind
40
How are plants adapted for pollination by insects?
- They have brightly coloured petals to attract insects
- They have scented flowers and nectaries to attract insects
- They make big, sticky pollen grains - stick to insects
- The stigma is also sticky - pollen stick to it
41
How are plants adapted for wind pollination?
- Small, dull pet as on the flower
- No nectaries or strong scents
- A lot of pollen grains - small and light to be carried by wind
- Long filaments that hang outside the flower, so a lot of pollen gets blown away
- A large, feathery stag,a to catch pollen as its carried by wind
42
What is fertilisation?
The fusion of gametes
43
Once the pollen has found its way to a stigma.. what happens?
fertilisation
44
What are the processes in fertilisation?
A pollen grain lands on stigma
A pollen tube grows out of pollen grain and down through style to the ovary
A nucleus from male gamete moves through tube to join with female gamete in the ovary
The two nuclei fuse together to make a zygote
45
Each fertilised female gamete forms...
a seed
46
In fertilisation.. the ovary develops into..
a fruit around the seed
47
What is artificial asexual reproduction called?
cloning
48
How do some plants reproduce asexually?
by growing new plants from their stems
| e.g strawberry plants send out runners sideways above the ground and take root
49
How can we clone plants?
Take cuttings and then plant these
50
What are male gametes in humans?
sperm
51
Where are sperm made?
in the testes, all the time after puberty
52
What do sperm mix with?
a liquid to form semen
53
When is sperm ejaculated from the penis into the vagina of a female?
during sexual intercourse
54
What is the urethra? (male)
a tube which carries sperm though the penis during ejaculation
and urine passes through it as well
55
What fills with blood to make penis erect?
erectile tissue
56
What produces the liquid thats added to sperm to make semen?
The glands
57
What is the tube called that carries sperm from the testis towards the urethra?
The vas deferens (sperm duct)
58
Where are sperm made?
in the testes
59
What contains the testes?
the scrotal sac
60
What are ova?
female gametes
61
When is an ovum produced from one of the two ovaries?
every 28 days
62
What happens after the egg (ova) is released from the ovaries?
It passes into the Fallopian tube - where it may meet sperm
63
What happens if an egg isn't fertilised by sperm?
The ovum will break up and pass out of the vagina
64
If an ovum is fertilised, what happens?
It starts to divide and the new cells will travel to the uterus (womb) and attach to the endometrium (uterus lining) and develop into an embryo
65
What is the muscular tube that carries the ovum from the ovary to the uterus called?
The Fallopian tube
66
What organ produces ova and sex hormones?
Ovary
67
What is the cervix?
The neck of the uterus
68
What is the vagina?
where the sperm are deposited
69
What does oestrogen in women cause?
Extra hair on underarms and pubic area
hips to widen
development of breasts
ovum release and start of periods
70
What does testosterone in men cause?
```
extra hair on face and body
muscles to develop
penis and testes to enlarge
sperm production
deepening of voice
```
71
What are the four stages of the menstrual cycle?
1. Bleeding starts - uterus breaks down for about 4 days
2. Uterus lining builds up again - day 4 to 14
3. At day 14 an ovum develops and is released
4. The wall is maintained for about 14 days until day 28
72
What does progesterone do?
maintains the lining of the uterus
73
What does oestrogen do?
causes the lining of the uterus to thicken and grow
74
What hormone stimulates the release of an ovum at day 14?
LH
75
What happens if a woman becomes pregnant?
The level of progesterone stays high to maintain the lining of the uterus during pregnancy
76
What are alleles?
different versions of the same gene
77
What is a dominant allele?
An allele which will always show up in the offspring
78
What is a recessive allele?
An allele which only shows if the individual has two copies of the recessive allele
79
What is meant if an organism is homozygous for a characteristic?
both alleles are the same
80
What is meant when an organism is heterozygous for a characteristic?
It has two different alleles
81
What does the phenotype describe?
The physical characteristics of an organism
82
What does the genotype describe?
the alleles that a cell or organism has for a particular feature.
83
When does codominance occur?
when neither allele is dominant and both contribute to the appearance of an offspring
84
What is the sex of a person controlled by?
The sex chromosomes
85
How can you show the possible alleles in the offspring?
Genetic diagrams or Punnet square
86
How many paired matches of chromosomes are there in every human body cell?
23
87
What chromosomes do all men have?
An X and a Y chromosome
88
What chromosomes do all women have?
two X chromosomes
89
Is there an equal chance of having a boy or a girl?
YES
90
What is genetic variation caused by?
genes
91
What is variation in animals caused by?
genetic and environmental factors
92
Name some genetic variation factors
- eye colour
- hair color
- inherited disorders
- blood group
93
What environmental factors are plants affected by?
sunlight
moisture level
temperature
mineral content in soil
94
What is the theory of evolution?
Life began as simple organisms from which more complex organisms evolved
95
What does natural selection mean?
Survival of the fittest
96
How does natural selection work?
Living things show variation
The resources living things need to survive are limited - individuals must compete for these resources to survive - only some will
Some of the varieties will have a better chance of survival
This means that a greater proportion os individuals in the next generation will have better alleles and the characteristics that help survival
Over many generations, the species become better and better able to survive and the 'best' features are naturally selected and the species become more and more adapted to its environment
97
What are mutations?
changes to the genetic code
98
How often does a gene mutate?
occasionally
99
What do mutations do?
change the sequins of the DNA bases
100
Are mutations usually harmful?
yes
101
What happens if a mutation occurs in reproductive cells?
The offspring may develop abnormally or die
102
What happens if mutation occurs in body cells?
The mutant cells may start to multiply in an uncontrolled way and invade other parts of the body (cancer)
103
How can bacteria evolve?
by becoming anti-biotic resistant
