7) Reproduction and Inheritance Flashcards
How many chromosomes does a human have?
46
What is a gene?
A gene is a chemical instruction that codes for a particular protein. Genes control our inherited characteristics
What are different versions of the same gene called?
Alleles
What is DNA?
A DNA molecule has two strands in the shape of a double helix.
What are the four different bases in DNA?
- (A) Adenine
- (C) Cytosine
- (G) Guanine
- (T) Thymine
How are the four different bases joined up? And what is this called?
A=T
C=G
This is called complementary base-pairing
What type of acid is DNA?
Nucleic
What is asexual reproduction?
Asexual reproduction involves only one parent. The offspring have identical genes to the parent - so there’s no variation between parent and offspring
What is mitosis?
Mitosis is when a cell reproduces itself by splitting to form two cells with identical sets of chromosomes
Apart from asexual reproduction, how else is mitosis useful?
Its how all plants and animals grow and repair dead tissue
What is sexual reproduction?
It involves the fusion of male and female gametes, because there are two parents contain a mixture of their parents’ genes
What is meiosis?
Meiosis produces four haploid cells whose chromosomes are not identical
What is the male and female reproduction part of the flower?
Male part= The stamen
Female part= The carpel
What does the stamen consist of and what do they do?
The anther= contains pollen grains
The filament= stalk that supports the anther
What does the carpel contain and what do they do?
Stigma= the pollen grains attach to it Style= the rod-like section that supports the stigma Ovary= Contains the female gametes (eggs)
What is pollination?
Is the transfer of pollen from anther to a stigma, so that the males gametes in sexual reproduction
What is cross-pollination?
Cross pollination is a type of sexual reproduction where pollen is transferred from the anther of one plant to the stigma of another
What do plants that cross-pollinate rely on?
Things like insects or the wind
What are the four things that plants can do to adapt for insect pollination?
1) Have brightly coloured petals to attract insects
2) Have scented flowers
3) They make big, sticky pollen grains, they stick to insects as they go from plant to plant
4) The stigma is also sticky so that any pollen picked up by insects on other plants will stick to the stigma
Name five things that plants can do to adapt for wind pollination?
1) Small dull petals on flower
2) No strong scents
3) A lot of pollen grains (small and light)
4) Long filaments that hang the anthers outside the plant
5) A large feathery stigma to catch pollen
What is fertilisation?
It is the fusion of gametes
What is sperm?
Sperm are male gametes, they are made in the testes, all the time after puberty
What is the urethra in a male?
A tube which carries sperm through ejaculation. Urine also passes through to exit the body
What are the glands for in a male?
Produce the liquid that’s added to sperm to make semen.
What is the erectile tissue?
Swells when filled with blood to make the penis erect
What are the vas deferens (sperm duct)?
Muscular tube that carries sperm from the testis towards the urethra
What are the testis for?
Where the sperm are made
What is the scrotum for?
Hangs behind the penis and contains the testes
What is the fallopian tube?
A muscular tube that carries the ovum from the ovary to the uterus
What is the uterus (womb) ?
The organ where an embryo grows
What is the ovary?
The organ that produces ova and sex hormones
What is the endometrium (lining of the uterus) ?
Has a good blood supply for implantation of an emybro
What is the cervix?
The neck of the uterus
What is the vagina?
Where the sperm are deposited
Explain the cycle of an egg
1) An ovum (egg) is produced every 28 days
2) It then passes into the fallopian tube
3) If it isn’t fertilised by sperm the ovum will break up and pass out of the vagina
What is the hormone that causes puberty in females?
Oestrogen
What is the hormone that causes puberty in males?
Testosterone
What happens to a female when she begins puberty?
- Extra hair on underarms and pubic hair
- Hips widen
- Development of breasts
- Ovum release and start of periods
What happens to a male when he begins puberty?
- Extra hair on face and body
- Muscles to develop
- Penis and testicles to enlarge
- Sperm production
- Deepening of voice
Explain the four stages of the menstrual cycle
Stage 1= Day 1 when bleeding starts. The uterus lining breaks down for about four days
Stage 2= The uterus lining builds up again from day 4 to day 14, into a thick layer of blood vessels, ready to receive a fertilised ovum
Stage 3= An ovum develops and its released from the ovary at day 14
Stage 4= The wall is maintained till day 28, if no fertilised egg has been received then the whole cycle starts again
What are the main effects of oestrogen?
- Causes the lining of the uterus to thicken and grow
- Stimulates the release of an ovum at day 14
What is the main effect of progesterone?
Maintains the lining of the uterus. When the level of progesterone falls, the lining breaks down
What is the main job of the placenta?
Once the embryo has implanted the placenta develops - this lets the blood of the embryo and the mother get very close to allow the exchange of food, oxygen and waste
What is the theory of evolution?
Life began as simple organisms from which more complex organisms evolved
What are mutations?
Mutations are changes to the genetic code. They are usually harmful
