Reproduction and inheritance Flashcards
What does the nucleus of a cell contain?
Chromosomes
What do chromosomes contain?
Long lengths of DNA coiled up
What’s a gene?
Short section of DNA
What are human body cells?
Diploid
What does diploid mean?
2 copies of each chromosome arranged in pairs.
What’s the diploid number (number of chromosomes) in humans?
46
What do genes do?
Chemical instructions which control our inherited characteristics
What’s an allele?
Different versions of the same gene
Describe the structure of DNA
Double Helix
Has complementary base pairing, Adenine to Thymine, and Cytosine to Guanine
Type of nucleic acid
What’s asexual reproduction?
involves one parent, offspring have identical genes to the parent, so there’s no variation
What is mitosis?
When a cell reproduces genetically identical cells, by splitting to form 2 cells with identical sets of chromosomes
Describe the process of Mitosis?
DNA duplicates
DNA forms X shaped chromosomes, each arm is an exact duplicate of the other
Chromosomes line up and cell fibres pull them apart, two arms go to each opposite side
Membranes form around the sets of new chromosomes, making nuclei
Creating 2 new genetically identical cells
What mitosis also be used for?
Making new cells for growth and repair
What’s sexual reproduction?
The fusion of male and female gametes to form a zygote. Because there are 2 parents the offspring contain a mixture of their parent’s genes
What’s a zygote
Fertilised egg
What are gametes?
Haploid
How many chromosomes are in a haploid gamete?
23
What’s meiosis?
Produces 4 haploid cells whose chromosomes aren’t identical
Describe the process of meiosis?
Duplicates DNA
Chromosomes line up in pairs at the centre of the cell
Pulled apart so each new cell will have some of fathers chromosomes and mothers
Chromosomes line up again, arms are pulled apart, creating 4 haploid cells
The structure of the flower?
P54
What’s the Stamen?
Male reproductive part of the plant
What’s part of the Stamen?
Anther and filament
What is the anther?
Contains pollen grains, which produce male gametes
What is the filament?
Stalk which supports anther
What’s the Carpel?
Female reproductive part of the flower
What’s in the Carpel?
Stigma, Style and ovary
What does the Stigma do?
The part in which the pollen grains attach to
What does the style do?
Supports the stigma
What does the Ovary do?
Contains the female gamete in ovules
What’s pollination?
Transfer of pollen from stigma to anther, so male gametes can fertilise female gametes in sexual reproduction
What’s cross pollination?
When the pollen is transferred from the anther of one plant to the stigma of another, this relys on insects or wind
How are plants adapted for wind pollination?
Brightly coloured petals to attract insects
Scented to attract insects
Big sticky pollen grains to attach to insects
Stigma is sticky to receive pollen
How are plants adapted for wind pollination?
Light pollen to be carried away by wind
Long filaments to expose pollen to the wind
Large feathery Stigma to catch pollen
What’s fertilisation?
When 2 nuclei fuse together to form a zygote, this divides by mitosis to form an embryo
Describe fertilisation in a plant?
Pollen grain lands on stigma
Pollen tube grows out of pollen grain through the style, to the ovary and into the ovule
A nucleus from the male gamete moves down the tube to fertilise with the female gamete
Each fertilised female gamete forms a seed, the ovary develops into a fruit around the seeds
What’s germination?
When a seed starts to grow
What are the right conditions for germination?
Water- to activate enzymes that break down food reservoirs
Oxygen- for respiration to grow
Suitable temperature- for the enzymes to work
How does a germinating seed get energy from it’s food stores?
Gets glucose from it’s food stores for respiration
Once it’s grown enough it can get it’s own energy by having leaves for photosynthesis
How can plants reproduce asexually using natural methods?
Runners (fast growing stems), take root somewhere and form clones
How can plants be reproduced artificially?
Take cuttings from one plant, and plant them somewhere else
What’s sperm?
Male gametes, formed in the testes after puberty, mixed with liquid to form semen and are ejaculated from the penis into the vagina in sexual reproduction
What’s the structure of the male reproductive system?
P57
What’s the urethra?
Urine and semen passes through it
What’s erectile tissue?
Swells with blood to make penis erect
What are the testis?
Where sperm are made
What are the glands?
Produce the liquid which is added to sperm to make semen
What’s the sperm duct?
Tube that carries the sperm to urethra
What’s the scrotum?
Contains the testes
Structure female reproductive system?
P 57
What are ova?
Female gametes produced once every 28 days from the one of the 2 ovaries
Describe the journey of an ovum?
Released from an ovary
Passes through the Fallopian tube where it could meet sperm
If not fertilised by sperm, it will break up and pass out of the vagina
If fertilised, the ovum will start to divide, the new cells which travel to uterus and attach to endometrium and turn into an embryo
What’s the fallopian tube?
Tube which carries ovum from ovaries to uterus
What’s the ovary?
Produces ova and sex hormones
What’s the endometrium?
Location for implantation of an embryo, has a good blood supply
What’s the uterus?
Where an embryo grows
What’s the vagina?
Where the sperm are deposited
What’s the cervix?
The neck of the vagina
What does oestrogen in women cause?
Pubic/underarm hair
Hips widen
Development of breasts
Ovum release and start of periods
What does testosterone in men cause?
Hair on face and body Muscles develop Penis and testis enlarge Sperm production Voice deepens
What’s stage 1 in the menstrual cycle?
Uterus lining breaks down causing bleeding (4 days)
What’s stage 2 in the menstrual cycle?
Uterus builds up ready to receive an egg ( 4-14 days)
What’s stage 3 in the menstrual cycle?
An ovum is developed and released (day 14)
What’s stage 4 in the menstrual cycle?
Uterus wall is maintained and breaks down if no fertilised ovum lands (14-28)
What does Oestrogen do?
Causes lining of uterus to thicken and grow
Stimulates the release of an ovum at day 14
What does progesterone do?
Maintains the lining of the uterus
What does the Placenta do for the embryo?
Good blood flow and very close blood channels, allows food, oxygen and waste to be transferred
What does the amniotic fluid do for the embryo?
Fluid protects embryo from bumps
What’s an allele?
A different version of a gene
How many alleles are in a gene?
2
What’s do alleles show?
Characteristics
What’s a dominant allele?
Will act over the recessive allele (capital letters)
What’s a recessive allele?
Will only show if both alleles are recessive (little letters)
What does homozygous for a trait mean?
Both alleles are the same eg. RR or rr
What does it mean if your heterozygous for a trait?
Both alleles are different eg. Rr
What’s a genotype?
The genes alleles you have
What’s a phenotype?
The characteristics an allele produces
How to work out possible alleles of offspring?
Punnet squares
What do your chromosomes determine?
Your gender, (by the 23rd pair)
What chromosome do all men have?
XY
What chromosome do all women have?
XX
What the chance of having a boy or girl?
50:50
What’s genetic variation caused by?
Genes
What’s variation in animals down to?
Genes and environment
What environmental variation is there in plants?
Sunlight
Moisture level
Temperature
Mineral content of soil
What’s the theory of evolution?
Life began as simple organisms from which more complex organisms evolved
What’s natural selection?
Survival of the fittest
What happens to the best genes for a particular environment?
They survive
What are mutations?
Changes in the genetic code, random and rare but can be inherited increasing variation
What increases the chances of cell mutation?
Ionising radiation
Chemicals called mutagens
Why are mutagens harmful?
If in reproductive cells, kills offspring
Can cause cancer
How can mutations be useful?
eg. might make a bacteria cell protected against Antibiotics, these reproduce passing this gene on, these are called superbugs
