reproduction Flashcards
what are the two types of reproduction?
Two types of reproduction are sexual and asexual
how many parents does asexual reproduction need?
Asexual repro only involves one parent whereas sexual requires two
what is a zygote
a fertilised egg cell
what type of organisms reproduce asexually 4
plants, fungi, bacteria and body cells reproduce asexually
what 3 things happen in asexual reproduction
in asexual reproduction:
1)The cells divide by mitosis
2)There is no fusion of gametes, no mixing of genetic information, and so no variation
3)produces clones –> the offspring are genetically identical to the parents
how are gametes formed
Gametes are formed by the cell division meiosis
what are gametes
sex cells
how many chromosomes do sex cells have (explain)
Each sex cell has half the original number of chromosomes, so that upon fusion, the original chromosome number is restored
what are the gametes in plants
In plants, the gametes are egg cells and pollen
what does sexual reproduction do to a species
Sexual reprodution introduces variation
what does haploid mean
Haploid = (ha-half) a cell with half the number of chromosomes
what does diploid mean
Diploid = a cell with the full set of chromosomes
what are alleles
Alleles = different forms of the same gene
in asexual reproduction is there any variation
In asexual reproduction there is NO variation
how many cells does mitosis produce
Where mitosis produces two identical cells,
how many cells does meiosis produce
meiosis produces four cells that are different.
what happens in meiosis 3
In meiosis:
1)the chromosomes are duplicated so there are four sets of chromosomes, and each chromosome forms a pair of chromatids
2)Cell divides twice to form four gametes each with a single set of chromosomes
3)Gametes contain random mixtures of original chromosomes, which introduces variation
visual representation of meiosis
https://www.youtube.com/watch?v=EEeMCNwowJg
advantages of meiosis 3
Asexual reproduction is more energy and time efficient as
there’s no need to find a mate or spread gametes
It is also a lot faster and produces large numbers of identical offspring
disadvantages of asexual reproduction
if the environment changes and one organism can’t survive, none can (as they are identical)
uses of asexual reproduction
Humans use/speed up asexual reproduction to produce large numbers of clones, for example in food production
advantage of sexual reproduction
In sexual reproduction, variation means that even if the environment changes, variation will alllow some animals to survive and reproduce –> natural selection
name 2 bodies of spores
Toadstools and puffballs are asexual fruiting bodies full of spores
what are the mass of thin threads called
Many fungi are made of a mass of thin threads called hyphae that form from the structures we see
when do fungi reproduce asexually
When conditions are NOT good, fungi reproduce asexually
how do fungi reproduce asexually
two hyphae from different fungi join and their nuclei fuse
what is pollination
Pollination = the process in which pollen from one flower must meet the female parts of another flower.
how do animals cause pollination?
Animals pollinate - insects, birds and bats –> carry the pollen/ make it easy to get carried by the wind, so plants are adapted to attract them
what are the advantages of plants being able to reproduce asexually
Plants being able to asexually reproduce means that even if plants don’t get pollinated, get eaten or are destroyed by frost, new plants can still form
where in the human body and what type of reproduction do malarial parasites use
malarial parasites reproduce asexually in human liver cells and blood cells
what happens to some parasites when the temperature drops
the drop in temperature from humans to parasites triggers some parasites to sexually reproduce
3 reasons why the genome matters
helps us understand inherited/genetic disorders like cystic fibrosis and sickle cell disease –> higher chance of overcoming them
linked to increased risk of developed many diseases so helps predict the risk for each individual
understanding it helps us learn more about evolution and history - family trees can be traced back using genome sequences
what is the backbone of dna made of
DNA backbone is made out of sugar and phosphate
whats the monomer of polynucleotide
its monomer is nucleotide
whats the name of dnas polymer
DNA is a polynucleotide
what would happen if a mutation in a single group of bases were too occur
A mutation in a single group of bases can lead to a change in the protein structure and the way it works
what are the steps to protien synthesis
Genes produce a template for protein –> reflects the sequence of bases in DNA, but is small enough to leave the nuclear pores
Template leaves the nucleus and binds to the surface of ribosome
Cytoplasm has carrier molecules each attached to an amino acid, which attach to the templates in the correct order given by DNA
Amino acids are joined together to form a specific protein
Carrier molecules continue bringing the specific amino acids in the correct order until template is completed
Protein detaches itself from the carrier molecules which detach from the template to be available to pick up more amino acids
completed protein chain folds up to form a unique shape which will help it carry out its function
what three things make a nucleotide
nucleotide is a part of the backbone with the base attached to it - it is a sugar, a phosphate and a base
what is the meaning of phenotype
Phenotype = the physical properties or physical make up of an organism
does mutation in the non coding part of the DNA change the phenotype directy
Mutations in the non-coding part of DNA does not directly change the phenotype
variants in the DNA cause?
BUT variants in non coding DNA can affect which genes are switched on and off - by changing the genes that are expressed, this can have a big effect on the phenotype
when are genes expressed
A gene being expressed is when the protein that this gene codes for is synthesised in the cell
does the most of DNA code for protein
Most of DNA doesn’t code for protein
what does homozygous mean
Homozygous = when an individual has the same alleles for a characteristic
what does heterozygous mean
Heterozygous = when an individual has different alleles for a characteristic
what are dominant alleles
Dominant alleles = expressed in the phenotype even if only one is present
what are recessive alleles
Recessive alleles = only expressed in the phenotype in the absence of a dominant allele
what do sex chromosomes determine in humans
Sex chromosomes determine the sex of the baby
what are the sex chromosomes for males
In human males, the chromosomes are different - XY
what are the sex chromosomes for females
In human females the chromosomes are the same - XX
what is polydactyly
Polydactyly = when some babies are born with extra fingers or toes
what type of allele is polydactyly caused by
The most common form on polydactyly is caused by a dominant allele
what is cystic fibrosis
Cystic fibrosis = a genetic disorder that produces really thick and sticky mucus, and affects the lungs, the digestive system and the reproductive system
what are the effects of cystic fibrosis
The lungs can become clogged - impairing ventilation
The pancreas cannot secrete enzymes
The small intestine becomes blocked with mucus
Many people with cystic fibrosis are infertile
how do we treat cystic fibrosis
Treatments for cystic fibrosis: physiotherapy, antibiotics to keep the lungs clear of mucus and infections, enzymes that the pancreas can’t make are replaced, and drugs to thin the mucus
what type of allele causes cystic fibrosis
Is caused by a recessive allele
steps to Amniocentesis
Two ways to do this:
Amniocentesis = Amnio –> taking amniotic fluid (the fluid that the embryo is floating in)
Centesis –> centrifuge the fluid
this is carried out at 10-15 weeks of pregnancy - the cells taken from centrifuging can then be used for screening
steps to cvs
Chorionic Villus Sampling (CVS) = this is carried out between 10 and 12 weeks of pregnancy
You take a small sample of tissue from the placenta - this would provide fetal cells that can be used in screening
Both of these methods carry risks of miscarriage
steps to pre implantaion screening
Pre-implantation technique = Embryos in IVF can be tested before being impanted with the permission of the couple
Screening can sometimes give a false positive or a false negative –> leads to the termination of a healthy baby
Screening is expensive –> offered to people with genetic disorders in the family history
