reproduction and inheritance Flashcards
where are chromosomes found
in the nucleus
what does a nucleus contain
genetic information in the form of chromosomes
state –> chromosomes are long lengths of DNA coiled up
state –> a gene is a short section of DNA
what does it mean if the human body cells are diploid
they have two copies of each chromosome arranged in pairs
how many chromosomes are in a human cell chromosome
46
what is the diploid number for a humanity
46
state –> genes are chemical instructions
what is DNA
is a long list of instructions how to put an organism together and make it work
what makes up an organisms genome
all of an organisms DNA
each separate gene in a DNA molecule…
is a chemical instruction that codes for a particular protein
why are proteins important
they control most processes in the body. They also determine inherited charecteristics (eg eye colour, blood type(
by controlling the production of proteins, what do genes also control
inherited characteristics
state –> there can be different versions of the same gene, which give different versions of a characteristic.
what are the different versions of the same gene called
alleles
state –> DNA is a double helix
describe the shape of a DNA molecule
it has two strands coiled together in the shape of a double helix
what are the who strands held together by
by chemicals called bases
what are the 4 types of bases
adenenine, guanine, cyctosine, thymine
base pairs
cytosine, guanine
adenine, thymine
what is it called when the bases are paired
complementary base pairing
what does DNA control
the production of proteins in a cell
what are proteins made up of
chains of molecules called amino acids, each different protein has its own particular number and order of amino acids
what happens when the amino acid chain fold up
the amino acids chain fold up to give each protein a different specific shape which means each protein can have a different function
what codes for a particular protein
a section of DNA that codes for a particular protein is called a gene
what decides the order of amino acids in a protein
the order of bases that decides the order of amino acids in a protein
what is a codon
each amino acid is coded is coded for by a sequence of 3 bases in the gene
state –> each codon in a gene contains 3 bases
state –> there are 64 possible codons, since there are only 20 amino acids, some codons code for the same amino acid
state –> the amino acids are joined together to make proteins, following the order of bases in the gene
state –> each gene contains a different sequence of bases, which is what allows it to code for a particular protein
what are non coding regions
many regions of DNA are non coding, that means they do not code for any amino acids but despite this some of these regions are still involved in protein synthesis
where is DNA found
in the cell nucleus and cant move out of it because it is really big
what are the two stages of how proteins are made
transcription
translation
where are proteins made
in the cell cytoplasm by subcellular structures called ribosomes
state –> the cell needs to get the information from the DNA to the ribosome in the cytoplasm
what is mRNA made up of
a sequence of bases but it is shorter and only a single strand
what does mRNA use instead of thymine
uracil
what happens once the mRNA is bound to a ribosome
the protein can be assembled. this stage is called translation
how does the cell get the information from the DNA to the ribosome in the cytoplasm
by using a molecule called messenger RNA
RNA polymerase is the enzyme involved in …
joining together the base sequence to make mRNA. This stage of protein synthesis is called transcription
how does transcription work
- RNA polymerase binds to a region of non coding DNA in front of a gene.
- the two DNA strands unzip and the RNA polymerase moves along one of the strands of the DNA
- it uses the coding DNA in the gene as a template to make the mRNA. Base pairing between the DNA and RNA ensures that the mRNA is complementary to the gene
- once made the mRNA molecule moves out of the nucleus and joins with a ribosome in the cytoplasm
how does translation work
- amino acids are brought to the ribosome by another RNA molecule called transfer RNA
- the order in which the amino aids are brought to the ribosome matches the order of the codons in the in mRNA
- part of the tRNA’s structure is called an anticodon - it is complementary to the codon for the amino acid. The pairing of the codon and anticodon makes sure that the amino acids are brought to the ribosome in the correct order
- the amino acids are joined together by the ribosome. this makes a protein
what does asexual reproduction involve
mitosis
how can an ordinary cell make a new cell
by dividing in two. both new cells are genetically identical to the original cell. - they both contain exactly the same genetic information
how do some organisms produce offspring
by using mitosis. This is known as asexual reproduction
what organisms reproduce asexually
bacteria and plants
what is asexual reproduction
involved only one parent. The offspring have identical genes to the parent - so there is no variation between parent and offspring
what is mitosis
mitosis is when a cell reproduces itself by splitting to form two cells with identicsl sets of chromosomes
what happens when a diploid cell divides by mitosis
you get 2 cells that are both diploid
how does mitosis work
- in a cell that is not dividing, the DNA is all spread out in long strings
- if the cell gets a signal to divide, it needs to duplicate its DNA- so there is one copy for each new cell. The DNA forms X shaped chromosomes. each arm of the chromosome is an exact duplicate of the other
- the chromosome then line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell
- membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells
- lastly the cytoplasm divides
- you now have two new cells containing exactly the same DNA - they are genetically identical
what is sexual reproduction
is where genetic information from two organisms (father and mother) is combined to produce offspring which are genetically different to either parent
how does sexual reproduction involve gametes
- in sexual reproduction a mother and father produce gametes
what does it mean if gametes are haploid
it means they have half the number of chromosomes in a normal cell.
what would the haploid number be if in humans each gamete contains 23 chromosomes
the haploid number would be 23
how does sexual reproduction involve fertilisation
- at fertilisation a male gamete fuses with a female gamete to form a zygote. The zygote ends up with the full set of chromosomes
- the zygote then undergoes cell division (by mitosis) and develops into an embryo
- the embryo inherits features from both parents - it’s received a mixture of chromosomes from its mum and dad (and its the chromosomes that decide how you turn out
- the fertilisation of gametes is random - this produces genetic variation in the offspring
what is a zygote
a fertilised egg
what doe sexual reproduction involve
the fusion of male and female gametes. because there are two parents, the offspring contain a mixture of their parents’ genes
what does meiosis produce
4 haploid cells whose chromosomes are not identical
state –> gametes are produced by meiosis
meiosis is another type of…
cell division
how is meiosis different to mitosis
because it does not produce identical cells
in humans where does meiosis only happen
in the reproductive organs (ovaries and testes)
what is meiosis division 2
- in the second division the chromosomes line up again in the centre of the cell. the arms of the chromosome are pulled apart
- you get 4 haploid gametes. each gamete only has a single set of chromosomes. the gametes are genetically different
what is meiosis division 1
- before the cell starts to divide , it duplicates its DNA ( so there is enough for each new cell) one arm of each X shaped chromosome is an exact copy of the other arm#- in the first division in meiosis the chromosomes line up in pairs in the centre of the cell, one chromosome in each pair came from the organism’s mother and one came from its father
- the pairs are then pulled apart, so each new cell only has one copy of each chromosome. some of the fathers chromosomes and some of the mothers chromosomes go into each new cell.
- each new cell will have a mixture of the mothers and fathers chromosomes. mixing up the genes like this is rly important - it creates genetic variation for the offspring
how can plants be adopted for pollination by insects
- they have brightly coloured petals to attract insects#- they also have scented flowers and nectaries to attract insects
- they make big sticky pollen grains, the grains stick to insects as they go from plant to plant
- the stigma is also sticky so that any pollen picked up by insects on other plants will stick to the sigma
what are the features of plants that are adapted for pollination by wind
- small dull petals on the flower
- no nectaries or strong scents
- a lot of pollen grains - they are small and light so that they can easily be carried by the wind
- long filaments that hang the anthers outside the flower so that a lot of the pollen gets blown away by the wind
- a large and feathery stigma to catch pollen as it is carried past the wind. the stigma often hangs outside the flower too
fertilisation is the fusion of gametes
- a pollen grain lands on the stigma of the flower, usually with help from insects or the wind
- a pollen tube grows out of the pollen grain and down through the style to the ovary and into the ovule
- a nucleus from the male gamete moves down the tube to join with a female gamete in the ovule. fertilisation is when the two nuclei fuse together to make a zygote. this divides by mitosis to form an embryonic
- each fertilised female gamete forms a seed. the ovary develops into a fruit around the seed
germination is when seeds start to grow
- a seed will often lie dormant until the conditions around it are right for germination
what are the right conditions for needs to start germinating
water - to activate the enzymes that break down the food reserves in the seed
oxygen - for respiration , which transfers the energy from food for growth
a suitable temp - for the enzyms inside the seed to work
germinating seeds get energy from food stores
- a developed seed contains an embryo and a store of food reserves, wrapped in a hard seed coat
- when a seed starts to germinate, it gets glucose for respiration from its own food store. this transfers energy it needs to grow
- once the plant has grown enough to produce green leaves, it can get its own food for energy from photosynthesis
how to investigate the conditions needed for germination
- take 4 boiling tubes and put some cotton wool at the bottom of each one
- put 10 seeds on top of the cotton wool in each boiling tube
- leave the tubes for a few days then absorbed what has happened
how can plants reproduce asexually using natural methods
- some plants do so by growing new plants from their stems
cloning plants using artificial methods
- gardeners can take cuttings from good parent plants and then plant them to produce genetically identical copies of the parent plant
- these plants can be produced quickly and cheaply.
human reproductive system
puberty and the menstrual cycle
the menstrual cycle and pregnancy
