Reproduction Flashcards
explain mitosis
in mitosis, one cell divides into two identical daughter cells
what are the two gametes in humans
sperm cells
egg cells
which cells are smaller, sperm cells or egg cells?
sperm cells are much smaller than egg cells
in gametes chromosomes are not paired, they are single so how many single chromosomes do gametes have
23 single chromosomes
what type of cell division are gametes made in?
meiosis
meiosis produces unidentical cells what does this mean
every sperm cell and every egg cell produced is different.
Aside from in animals. where else does meiosis take place and what are the gametes in this case?
meiosis also takes place in flowering plants
in this case the gametes are pollen and egg cells
what are the key features of sexual reproduction
sexual production involves the fertilisation of male and female gametes.
as both every sperm cell and every egg cell are different, in sexual production there is mixing of genetic information.
the offspring recieves genetic information from both male and female parents
there is variation in the offspring
what is an aphid reproducing an example of
-asexual reproduction
asexual reproduction in the context of an aphid
in asexual reproduction there is only one parent so the aphid is the only parent of the offspring.
asexual reproduction does not involve gametes
because there is only one parent, there is no mixing of the genetic information so the offspring are all gentically identical.
these offsprings are known as clones
because asexual reproduction does not involve gametes, meiosis does not take place. asexual reproduction involves mitosis only.
asexual reproduction- one parent involved
only one parent so no mixing of genetic information
offspring are all genetically identical
offsprings are clones
another example of asexual reproduction are buds
buds drop off and grow into new plants
offspring plants are genetically identical to the parent - they are clones
how many single chromsomes do human gametes contain
23 single chromosomes
key steps of meiosis
-meiosis only takes place in reproductive organs such as the ovaries (females) and the testes.(males)
first stage of meiosis, all of the chromosomes are copied
cell now divides into two
now both of these cells divide one more time forming the gametes.
in the gametes the chromosomes are now singled and not paired.
meiosis has halved the number of chromosomes
meiosis produces 4 gametes from one original cell
each of these 4 gametes are gentically different from one another.
each gamete has different alleles
in sexual reproduction
-gametes join together- scientists call this fertilisation ( when a female gamete and a male gamete fuse)
after fertilisation, cell now has full number of chromosomes.
human sperm cell and human egg cell both contain 23 single chromosomes each but when fertilised, they contain 23 chromosome pairs.
what happens after fertilisation
the new cell divides by mitosis, producing a clump of identical cells. scientists call this clump of identical cells an embryo.
as the embryo develops the cells diffrentiate forming differnet types of cells. (nerve cells and muscle cells in animals)
where are chromosomes found
in the nucleus of cells
chromosomes contain a molecule called DNA. why do scientists say that DNA is our genetic material
that is because DNA determines are inherited features.
DNA consists of two strands what are these strands called
polymer chains
in dna the two strands wrap around each other to form a double helix.
what is the defintion of a gene
a gene is a small section of DNA on a chromosome.
proteins are made by joining together amino acids. each gene encodes for a specific sequence of amino acids to make a specific…
proteins are made by joining together amino acids. each gene encodes for a specific sequence of amino acids to make a specific protien.
blood type gene example
blood type gene encodes the sequence of amino acids for the protein that determines blood type.
humans have thousands of genes. do both chromsomes in a pair have the same genes or different genes.
both chromosomes in a pair have the same genes.
what is the definition of a genome
the genome is the entire genetic material of an organism. the human genome is the entire genetic material that makes a human.
what are some of the benefits of scientists studying the entire human genome?
- understanding the entire genome can help us search for genes that are linked to diseases. e.g genes that increase the risk of developing cancer or alzheimars disease.
- understanding the human genome will help us understand and treat inherited disorders such as cystic fibrosis.
- to trace human migration patterns from the past ( this helps people to discover their ancestory)
DNA STRUCTURE (triple biology) recap of DNA
- DNA is the genetic material
- DNA is contained in chromosomes in the nucleus.
- DNA is a polymer made up of two strands. the two strands wind around each other to form a double helix.