Flashcards in biology- reproduction and inheritance p2 Deck (95):
what does the nucleus contain?
your genetic material in the form of chromosomes
what are chromosomes?
long lengths of DNA coiled up
what is a gene?
a short section of DNA
what does diploid mean?
each cell has two copies of each chromosome, arranged in pairs
what is the diploid number for a human?
what is DNA?
a long list of instructions on how to put an organism together and make it work
what does each separate gene in a DNA molecule do/is?
is a chemical instruction that codes for a particular protein
why are proteins important?
they control most processes in the body. They determine inherited characteristics e.g. eye colour, blood type
by controlling the production of proteins, what also controls our inherited characteristics?
what are alleles?
different versions of the same gene
describe DNA structure
a DNA molecule has two strands coiled together in the shape of a doubles helix. The two strands are held together by chemicals called bases
what are the 4 bases in DNA, how do they pair?
adenine, cytosine, guanine, thymine : A-T and C-G
what is DNA a type of ?
what is mitosis?
when a cell reproduces itself by splitting to form two cells with identical sets of chromosomes
what are some organisms which produce asexually?
bacteria and plants
define asexual reproduction
it involves only one parent. The offspring have identical genes to the parent- so there's no variation between parent and offspring
what are the 6 stages of mitosis?
1) in a cell that's not dividing, the DNA is all spread out in long strings
2) if the cell gets a signal to divide, it duplicates its DNA- one copy for each new cell
- the DNA forms X-shaped chromosomes:each 'arm' of the chromosome is an exact duplicate of the other
3) the chromosomes line up at the centre of the cell and cell fibres pull them apart. the two arms go to opposite ends of the cell
4) membranes form around each of the sets of chromosomes. these become the nuclei of the two new cells
5) the cytoplasm divides
6) left with 2 new cells containing exactly the same DNA-genetically identical
what uses mitosis?
make new cells
growth and repair damaged tissues
what is sexual reproduction?
involves the fusion of male and female gametes. because there are 2 parents, the offspring contain a mixture of their parent's genes- they are genetically different
why are gametes haploid?
they have half the number of chromosomes in a normal cell. in humans gametes contain 23 chromosomes- haploid number is 23
what happens after fertilisation?
the zygote ends up with the full set of chromosomes and undergoes cell division by mitosis and develops into an embryo
how is genetic variation in the offspring produced?
because the fertilisation of gametes is random
meiosis produces four haploid cells whose chromosomes are not identical
what are the 6 stages of meiosis?
1) before the cell divides it duplicates its DNA. each chromosome is an exact copy of the other chromosome
2) in the 1st division, the chromosomes line up in pairs at the centre of the cell
3) the pairs are then pulled apart, so each new cell only has one copy of each chromosome. some father's and some of the mother's go into each cell
4)each new cell has a mixture of the mother's and father's chromosomes- creates variation in the offspring
5) in the 2nd division the chromosomes line up in the centre of the cell and the arms of each chromosome are pulled apart
6) you get 4 haploid gametes- each has only a single set of chromosomes. The gametes are all genetically different
what's the male reproductive part in a plant called and what does it consist of?
the stamen- consists of the anther and filament
- anther contains pollen grains to produce the male gametes
- the filament is the stalk that supports the anther
what is the females reproductive part in a plant and does it consist of?
-stigma- the end bit that pollen grains attach to
- the style is the rod-like section that supports the stigma
- the ovary contains the female gametes
what is pollination?
the transfer of pollen from an anther to a stigma so that the male gametes can fertilise the female gametes
what is cross-pollination?
in sexual reproduction when pollen is transferred from the anther of one plant to the stigma of a different plant
how are plants adapted for insect pollination?
1) brightly coloured petals
2) scented flowers and nectaries
3) big, sticky pollen grains to stick to insects
4) stigma is sticky so pollen can stick to the stigma
how are plants adapted for wind pollination?
1) small, dull petals
2) no nectaries or strong scents
3) a lot of pollen grains- small and light so easily carried by the wind
4) long filaments that hang the anthers outside the flower-lots of pollen gets blown away by the wind
5) large and feathery stigma to catch pollen- hangs outside the flower to catch pollen
describe the 4 steps in plant fertilisation
1) a pollen grain lands on the stigma of a flower by wind or insects
2) a pollen tube grows out of the pollen grain and down through the style to the ovary
3) a nucleus from the males gamete moves down the tube to join the female gamete in the ovary. Fertilisation is when the 2 nuclei fuse together to make a zygote. This divides by mitosis to form an embryo
4) each fertilised female gamete forms a seed. The ovary develops into a fruit around the seed
how do plants reproduce asexually?
in strawberry plants, the parent plant send out runners= fast-growing stems that grow sideways just above the ground
the runners take root at various point and new plants start to grow
the new plants are clones of the parent strawberry plant, so no genetic variation between them
what do plants reproduce asexually using artificial methods?
-used to clone plants
1) gardeners take cutting from good parent plants, each with a new bud
2) the cuttings are kept in moist condition until they are ready to plant
3) then planted and produce genetically identical copies
- produced quickly and cheaply
in the penis, what happens to the erectile tissue during sex?
swells when filled with blood, to make the penis erect
what do the glands do in male sex organ?
produce the liquid that's added to sperm to make seme
what are vas deferens?
the sperm ducts- muscular tube that carries sperm from the testis towards the urethra
how does the female reproductive system make ova?
1) an ovum is produced every 28 days form one of the two ovaries
2) it passes into the fallopian tube where it might meet sperm that have entered during sex
3) it isn't fertilised, the ovum will break up and pass out the vagina
4) if it is fertilised, the ovum starts to divide. The new cells will travel down the Fallopian tube to the uterus(womb) and attach to the endometrium (uterus lining). A fertilised ovum develops into an embryo
what's the Fallopian tube?
or oviduct- muscular tube that carries the ovum from the ovary to the uterus- fertilisation here
what are the ovaries?
the organ that produces ova and sex hormones
what's the cervix?
the neck of the uterus
what's deposited in the vagina?
what is the endometrium?
the lining of the uterus- has a good blood supply for implantation of an embryo
what does oestrogen cause?
1)extra hair on underarms and pubic area
2) hips to widen
3) development of breasts
4) ovum release and start of periods
what does testosterone cause?
1) extra hair on face and body
2) muscles to develop
3) penis and testicles to enlarge
4) sperm production
5) deepening of voice
what are the 4 stages of the menstrual cycle?
1) day 1 when bleeding starts. The uterus lining breaks down for about 4 days
2) the uterus lining builds up again from day 4 to day 14 into a thick spongy layer full of blood vessels ready to receive a fertilised ovum
3) an ovum develops and is released from the ovary at day 14
4) the wall is then maintained for about 14 days until day 28. if not fertilised ovum has landed on the uterus by then the spongy lining starts to break down and the whole cycle starts again
in the menstrual cycle what does oestrogen do?
1- causes the lining of the uterus to thicken and grow
2- stimulates the release of an ovum at day 14 from hormone called LH which oestrogen stimulates the production of
in the menstrual cycle what does progesterone do?
1-maintains the lining of the uterus
2- when the level of progesterone falls, the lining breaks down
what happens to the level of progesterone if an ovum gets fertilised?
it will stay the same to maintain the lining of the uterus during pregnancy
what are the stages of pregnancy?
what's the dominant allele?
the version of the characteristic that appears
what is the recessive allele?
the version of the characteristic that doesn't appear unless both alleles are recessive
most of the time you have 2 copies of each gene one from each parent, if the alleles are different then?
you have instructions for 2 different versions of characteristic but you only show one version.
if you're homozygous for a trait, what do you have?
two alleles the same for that particular gene so DD of dd
if you're heterozygous for a trait, what do you have?
two different alleles for that particular gene so Dd
what is your genotype?
the alleles you have
what is your phenotype?
the characteristics the alleles produce
what do two parent genotypes of Bb create gametes, genotypes, and phenotypes of if B stands for brown eyes and b stands for blue eyes?
parents' phenotypes: brown and blue x2
parents' genotypes: Bb Bb
gamete's genotypes: B b B b
offsprings' genotypes: BB Bb Bb bb
offsprings' phenotypes: brown brown brown blue
75% chance the offspring have brown eyes
what is a monohybrid cross?
when you breed two organisms together to look at one characteristic
what are people called who have one copy of the recessive allele?
all men have what types of chromosomes and what do they cause?
X & Y= XY. the Y chromosome causes male charcteristics
all women have what types of chromosomes and what do they cause?
two X chromosomes: XX
the XX combination causes female charcteristics
what is the chance of having a boy or a girl?
what is most variation in animals due to?
genes and environment
what factors aren't affected by the environment?
1- eye colour
2- hair colour
3- inherited disorders
4- blood group
what can a baby's weight at birth be affected by?
the mother's diet
what can having a poor diet whilst your growing up do?
stunt your growth
what effects health?
genes- some more likely to get certain diseases
environment- lifestyle affects the risk e.g. smoking, junk food
what effects intelligence?
genes- maximum IQ determined
environment- getting max IQ depends on environment- upbringing/ school
what affects sporting ability?
genes- determine potential
environment- have to train
variation in plants due to the environment?
2- moisture level
4- mineral content of the soil
what is the theory of evolution?
life began as simple organisms from which more complex organisms evolved
what are the stages of natural selection?
1- living things show variation
2- the resources living things need to survive are limited so individuals must compete for these resources to survive so only some individuals will survive
3- some of the varieties of a species will have a better chance of survival which increases the chance of breeding and passing on their genes
4- so greater population of individuals in the next generation with better alleles, and so the characteristics, that help survival
5- over many generations, the species becomes better and better able to survive. the 'best' features are naturally selected and the species becomes more and more adapted to its environment
what is a mutation?
a rare, random change in an organism's DNA that can be inherited
what do mutations change?
the sequence of the DNA bases. this could stop the production of a protein, or it might mean a different protein is produced instead. This can lead to new characteristics, increasing variation.
are mutations usually good or harmful?
harmful- if a mutation occurs in reproductive cells, the offspring might develop abnormally or die
- if a mutation occurs in body cells, the mutant cell may start to multiply in an uncontrolled way and invade other parts of the body- which is cancer
what happens to mutations with no effect? where do they happen?
occur in unimportant parts of the DNA- these are said to be neutral
how can mutations be beneficial?
give an organism a survival chance so can live in conditions where others die. e.g. a mutation in a bacterium might make it resistant to antibiotics. if this mutant gene is passed on you might get a resistant 'strain' of bacteria which antibiotics can't kill
bacteria can evolve to become what?
how does antibiotic-resistance work?
random mutation in bacteria DNA leading to changes in their characteristics- so can resist antibiotics.it lives longer and reproduces more so leads to the gene for resistance being passed on to lots of offspring = natural selection. it become more common in a population of bacteria over time.
big problem as people who became infected with these can't get rid of them easily. sometimes companies make a new antibiotic that's effective but 'superbugs' that are resistant to most know antibiotics (MRSA) are becoming more common
What is MRSA?
a type of bacterial infection that is resistant to a number of widely used antibiotics.
what is germination?
when seeds start to grow
until when will the seeds lie dormant?
until the conditions are right for germination
what are the conditions needed for seeds to start germination and why?
1) water- to activate the enzymes that 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 but depends on the type of seed
how does a seed germinate?
1- the seed takes in water and starts to grow using its store of energy
2- the first root starts to grow down into the soil
3- the shoot grows up
4- finally, extra roots grow and the first green leaves appear
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 from its own food store. This gives it the energy it needs to grow
3- once the plants has grown enough to produce green leaves, it can get its own food for energy from photosynthesis
how does an embryo develop during pregnancy?
once an ovum has been fertilised, it develops into an embryo and implants in the uterus. In later stages of pregnancy the embryo is called a fetus
1- once the embryo has implanted, the PLACENTA develops- this lets the blood of the embryo and mother get very close to allow the exchange of food, oxygen and waste
2- the amnion membrane forms- this surrounds the embryo and is full of amniotic fluid. Amniotic fluid protects the embryo against knocks and bumps
what does the placenta exchange?
food, oxygen and waste
what does amniotic fluid do?
it protects the embryo against knocks and bumps
what are codominant alleles?
neither allele is recessive, so you show characteristics from both alleles
give an example of when codominant alleles show
not blood group A or B but blood group AB
what is your blood type determined by?
two codominant alleles- A and B and one recessive O
what can the blood types be?
type A- AA AO
type B- BB BO
type AB - AB
type O- OO
how are the chances of mutation increased?
mutations can happen spontaneously- when a chromosome doesn't quite copy itself properly: a chance of mutation is increased by exposing yourself to:
1- ionising radiation- X-rays, gamma rays or UV light
2- chemicals called mutagens, e.g. chemicals in tobacco
what are chemicals called that lead to mutation?