genetics Flashcards
what is sexual reproduction
where genetic information from 2 organisms is combined to produce offspring which are genetically different to either parent
what is a gamete
reproductive cells
examples of reproductive cells
sperm
egg
what is a haploid cell
half the number of chromosomes in the normal cell
examples of diploid cells
gametes (sperm and eggs)
what happens during fertilisation
a male gamete fuse with a female gamete to produce a fertilised egg, also known as a zigote. The zygote sperm ends up with the full set of chromosomes (so it is diploid).
The embryo inherits characteristics from both parents, as it has received a mixture of chromosomes (and therefore genes) from its mum and its dad.
what is a zygote
female gamete which produces a fertilised egg
how are gametes produced
meiosis which only happens in reproductive organs
what happens during meiosis
DIVISION 1:
1) Before the cell starts to divide, it duplicates its DNA (so there’s enough for each new cell). One arm of each X-shaped chromosome is an exact copy of the other arm.
2) In the first division in meiosis (there are two divisions) 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.
3) The pairs are then pulled apart, so each new cell only has one copy of each chromosome. Some of the father’s chromosomes and some of the mother’s chromosomes go into each new cell.
4) Each new cell will have a mixture of the mother’s and father’s chromosomes. Mixing up the genes like this is really important it creates genetic variation in the offspring.
DIVISION 2:
5) In the second division the chromosomes line up again in the centre of the cell. It’s a lot like mitosis. The arms of the chromosomes are pulled apart.
6)You get four haploid daughter cells - these are the gametes. Each gamete only has a sinole set of
chromosomes. The gametes are all genetically different.
what is asexual reproduction
divide by mitosis, results in two diploid daughter cells, which are genetically identical to each other and to the parent cell
what is sexual reproduction
involves meiosis and the production of genetically different haploid gametes, which fuse together to form a diploid cell
asexual reproduction advantages
- produce lots of offspring quickly as it’s independent
e.g. bacteria E. coke can divide every half an hour - only one parent is needed, can happen whenever without waiting
asexual reproduction disadvantages
- no genetic variation
- if environment changes and conditions become unfavourable, the whole population may be affected
sexual reproduction advantages
- creates genetic variation
- if environment changes, more chance some will survive
- can lead to natural selection and evolution
sexual reproduction disadvantages
- takes more time and energy
- two parents are needed, can be a problem if one is isolated
what is DNA made up of
polymers made up of lots of repeating units called nucleotides
what is a nucleotides
one sugar molecule, one phosphate molecule and one base
what are the 4 bases called
adenine
thymine
cytosine
guanine
what bases pair together
A,T
G,C
how is DNA stored
chromosomes which contain genes
how do you extract DNA from fruit
1)Mash some strawberries and then put them in a beaker containing a solution of detergent and salt. Mix well. The detergent will break down the cell membranes to release the DNA. The salt will make the DNA stick together.
2) Filter the mixture to get the froth and big, insoluble bits of cell out.
3) Gently add some ice-cold alcohol to the filtered mixture.
4) The DNA will start to come out of solution as it’s not soluble in cold alcohol. It will appear as a stringy white precipitate (a solid) that can be carefully fished out with a glass rod.
how are proteins made
by reading the code in DNA
what is a mutation
a rare, random change to an organisms DNA base sequence which can be inherited
what is a genetic variant
a different version of the gene
what is an amino acid
protein chains
what is transcription
the process by which a cell makes an RNA copy of a piece of DNA which then carries the genetic information needed to make proteins in a cell. It finally carries the information from the DNA in the nucleus of the cell to the cytoplasm, where proteins are made.
what is translation
the process by which a cell makes proteins using the genetic information carried in messenger RNA which then is made by copying DNA, and the information it carries tells the cell how to link amino acids together to form proteins.
what does non-coding do
binding of RNA polymerase
what is the pea plant experiment
- In one experiment, Mendel crossed two pea plants of different heights - a tall pea plant and a dwarf pea plant. The offspring produced were all tall pea plants.
- He then bred two of these tall offspring together. He found that when the offspring from the first cross were crossed with each other, three tall offspring were produced for every one dwarf offspring overall. In other words, he produced a 3 : 1 ratio of tall : dwart plants.
what were mendel’s 3 important conclusions
- characteristics in plants are determined by ‘hereditary units’
- hereditary units are passed on to offspring unchanged from both parents, one unit from each parent
- they can be dominant or recessive, if there is both the dominant will be displayed
what is an allele
different versions of the same gene
homozygous
the two alleles of the particular gene is the same
heterozygous
the two alleles of the particular gene is different
how is a dominant allele shown
D (capital)
how is a recessive gene shown
r (mini)
what is your genotype
combination of alleles you have
what is your phenotype
alleles determine what characteristics you have, the combinations of alleles give rise to different phenotypes
what is monohybrid inheritance
inheritance of a single characteristics, can be used to show how recessive and dominant traits for a single characteristic
what can a genetic diagram show
how sex is determined in humans
how many pairs of chromosomes are found in every human body cell
23 matching pairs
what is the symbol of female chromosomes
XX
what is the symbol of male chromosomes
XY
example of genetic disorder
cystic fibrosis which is recessive
why do alleles arise
due to genetic mutations
what is a mutation
changes to the base sequence of DNA
what do mutations have an effect on
phenotype
what is the human genome project
thousands of scientists from all over the world worked together to find every single human gene. found the locations of around 20,500 genes.
prediction and prevention of diseases
many diseases are caused by the interaction of different genes
e.g. if they knew what genes did what to people they could tailor a lifestyle for them
testing and treatment for disorders
inherited disorders are caused by the presence of one or more faulty alleles in a persons genome, they can identify disorders much more quickly than the past.
new and better medicine
they can design new drugs which are tailored to different people with a particular genetic variation
what are the 3 drawbacks to the human genome project
- increased stress
- geneism
- discrimination
