B13 Reproduction Flashcards
(31 cards)
compare asexual and sexual reproduction
asexual
- cells divide by mitosis,
- offspring is genetically identical to (a clone of) parent: no variation,
sexual
- cells divide by meiosis to form gametes,
- gametes fuse to form a zygote,
- offspring inherits genetic information and characteristics from both parents: variation.
in which part of the body are gametes produced in animals?
e.g. for humans?
in the sex organs
e.g. testes and ovaries.
what are the animal
and the plant
gametes?
humans:
- female: egg cells,
- male: sperm
plants:
- female: egg cells,
- male: pollen.
describe the process of meiosis of a cell
- cell copies its genetic information, so that there are now 4 (rather than 2) sets of each chromosome which each forms a pair of chromatids,
- cell divides twice in quick succession to form four gametes, each with one set of chromosomes.
how many chromosomes does a human body cell have?
so how many chromosomes does a human gamete have?
46 (in 23 pairs)
gamete has 23
advantages + disadvantages of asexual reproduction
asexual
advantages
- time + energy efficient: one parent so no need to find a mate or spread gametes,
- no variation in offspring, can produce large amount of clones which can be useful e.g. in agriculture.
disadvantage
- introduces no variation: if there is an unfavourable change in the environment, no organisms of the species can survive.
advantages + disadvantages of sexual reproduction
asexual
advantage
- variation in offspring, higher chance of some surviving if there is a change in the environment, natural selection,
disadvantages
- time + energy inefficient: two parents so it takes energy and time to find a mate or spread gametes.
describe how malarial parasites reproduce
- asexually in human liver and blood cells,
- when mosquito takes blood meal, the drop in temperature triggers sexual reproduction in parasites in the red blood cells,
- for 20 mins, sexual forms burst from the blood cells and meet to form zygotes with 2 sets of chromosomes,
- zygotes undergo meiosis to produce new asexual parasites to infect a new human host.
what are chromosomes made of?
DNA
what are genes?
sections of DNA which store genetic information
each gene codes for…
each gene codes for a specific sequence of amino acids that forms a particular protein
what is the genome of an organism?
the sum of all the organism’s genetic material
why is studying the human genome important?
- helps us PREDICT and thus prevent the growth of DISEASES through lifestyle changes (since some genes are linked to certain diseases),
- helps us understand human evolution and history,
- helps us understand inherited disorders and how to overcome them.
what is a nucleotide?
what do they make up?
- nucleotide: the combination of a phosphate and a sugar, which is attached to a base (A, T, C or G),
- repeating nucleotide units make up the DNA polymer.
which bases always link up with each other in a DNA molecule?
A and T
G and C
(remember: AT Gemma Collins)
why are the links of bases together important for the functioning of a DNA molecule?
- they hold the structure of the DNA double helix together,
- they help the information from genes on DNA be translated into proteins in the cell.
describe the process of protein synthesis
- gene produces a template which reflects the order of bases given by DNA and is small enough to leave nucleus through pores in the nuclear membrane,
- template leaves nucleus and binds to surface of a ribosome,
- carrier molecules from cytoplasm attached to amino acids repeatedly bring and attach them to the template in the given order,
- until template is complete and a complete amino acid is formed,
- amino acids join together into proteins which are shaped for a specific function.
why does changing the order of bases in the DNA affect the protein that is formed during protein synthesis?
- changed order of bases in DNA means a different template is formed,
- meaning it gives a different order of amino acids which will produce a different protein being produced by a gene.
what is a mutation?
a change in an existing gene that results in a new gene
what is an allele?
a form of a gene which codes for a particular protein and combine with each other to determine an offspring’s characteristics.
how can a mutation affect the protein formed by a gene?
- most of the time only alter a protein’s appearance or function very slightly or not at all,
- sometimes a mutation can affect the shape of a protein which affects its function negatively (e.g. enzyme no longer binding to substrate) or positively (e.g. producing a more efficient enzyme).
what is a homozygote
and a heterozygote?
homozygote: has two identical alleles for a characteristic,
heterozygote: has two different alleles for a characteristic.
what is a genotype + example?
the alleles present in an individual regarding a particular characteristic,
e.g. Bb, bb.
what is polydactyly?
what kind of allele is it caused by?
an inherited disorder which causes extra toes or fingers,
caused by a dominant allele.
