Reproduction And Inheritance Flashcards
What does diploid mean and what is the number for the human body
Diploid means they have two copies of each chromosome, arranged in pairs
A human cell nucleus contains 46 chromosomes so the diploid number for humans is 46
Name the four different bases found in DNA
Adenine (A)
Cytosine (C)
Guanine (G)
Thymine (T)
How do bases found in DNA pair up
The bass are pairs and they always pair up in the same way it’s always:
A-T and C-G
Why does sexual reproduction result in offspring that are genetically different from either parent
Sexual reproduction involves the fusion of male and female gametes. Because there are two parents, the offspring contain a mixture (23 chromosomes from each) of their parents genes
Describe how and where meiosis takes place
In humans meiosis only happens in the reproductive organs (ovaries and testes)
Division 1:
1) before the cells begin division it duplicates its DNA so there’s enough for each new cell (each arms are exact copies of one another)
(Don’t understand rest)
Name male and female reproductive parts of the flower
Male:
Stamen- containing anther and filament
Female:
Carpel- containing ovary, style and stigma
Define pollination
Pollination is the transfer of pollen from an anther to a stigma, so that the male gametes can fertilise the female gametes in sexual reproduction
Give three differences between plants that are pollinated by insects and ones that are wind pollinated
Insect pollinated: Bright colour petal Scented flowers and nectaries Big sticky pollen grains Stigma is also sticky Wind pollinated Small dull petals No next aired Lots of pollen (small and light) Long filament that hang anthers outside flower so wind can blow pollen away Large feathery stigma to catch pollen, often hangs outside the flower too
Define fertilisation
Fertilisation is the fusion of gametes
Explain how the pollen gets from the stigma to the ovary
1) pollen grain lands on the stigma of a flower
2) pollen tube grows out of pollen grain and down through the style to the ovary and into the ovule
3) the nucleus from the male gamete moves down the tube to join with a female gametes in the ovule
4) fertilisation occurs then mitosis divides the zygote to form an embryo
What 3 conditions are needed for seed germination
1) water - to activate the enzymes and break down the food reserves in the seed
2) oxygen - for respiration which provides the energy for growth
3) a suitable temperature - for the enzymes inside the seed to work
How do germinating seeds get energy from food stores
1) a developed seed contains an embryo and a store of food reserves, wrapped in a hard seed coat
2) when a seed starts to germinate, it gets glucose for respiration
3) once the plant has grown enough to produce green leaves, it can get its own food for energy from photosynthesis
Give an example of a plant that reproduces asexually and briefly describe how it happens
Strawberry plants
1) the parent strawberry plant send out runners - fast growing stems that grow out sideways, just above the ground
2) the runners take root at various points (a short distance away)and new plants start to grow
3) the new planes are clones of the parents
Describe how to make plant clones from cuttings
1) gardeners can take cuttings from good parent plants to produce genetically identical copies
2) cuttings are taken each with a new bud on
3) the cuttings are kept in moist conditions until they are ready to plant
4) these plants can be produced quickly and cheaply
Where are sperm and the ova made in the human reproductive system?
Sperm are made in the testes
Ova are made in the ovaries
What secondary characteristic does testosterone trigger in makes
1) extra hair oh face and body
2) muscles to develop
3) deepening voice
What secondary characteristics doers oestrogen in females
Extra hair underarms and pubic area
Hips widen
Breasts
Periods
Describe the four stages of the menstrual cycle
Stage 1: day 1 is when bleeding starts - the uterus lining breaks down for about 4 days
Stage 2: the uterus lining builds up again from day 4-14 into a thick spongy layer full of blood vessels, ready to receive egg
Stage 3: ovum develops and is released from dat 1:
Stage 4: the wall is then maintained for 14 days until day 28
What role do oestrogen and progesterone play in the menstrual cycle
Oestrogen causes the lining of the uterus to thick and grow. It also stimulates the release of an ovum
Progesterone maintains the lining of the uterus. When the level of progesterone falls, the lining breaks down
What is the function of amniotic fluid in pregnancy
Amniotic fluid protects baby against knocks and bumps
What does it mean if you are homozygous for a particular trait
If you’re homozygous for a trait you have two alleles the same for that partially gene eg CC or cc
What are codominant alleles
Neither allele is recessive so you show characteristics from both alleles eg blood group A or B but blood groups AB
Which two chromosomes determine where you are male or female p
There are 23 matched pairs of chromosomes in every human body cell. The 23rd pair is labelled xx or xy. They’re the two chromosomes that decide whether you turn out male or female
List four features of animals which aren’t affected at all by their environment, and three which are
Aren't affected: Eye colour Hair colour Inherited disorder Blood group Affected: Growth Intelligence Spouting ability
What is the theory of evolution
Life began as simple organisms from which more complex organisms evolved
What is a mutation
Mutations are rare random changes to the genetic code/ organism’s DNA
Give and example of how a genetic mutation could be a) harmful b) beneficial
A) harmful- mutations occur in reproductive cells, the offspring might develop abnormally or die. If a mutation occurs in body cells the mutant cells stat to multiply in an uncontrolled way and invade other part of the body (cancer)
B) beneficial - mutations can be beneficial and give an organism a survival advantage, so it can live on in conditions where the others die. This is natural selection. Eg a mutation in bacterium might make it resistant to antibiotics
What is a Superbug
Superbugs are resistant to most known antibiotics such as MRSA
What is a gene
A short section of DNA
