TOPIC B6 INHERITANCE, VARIATION AND EVOLUTION Flashcards
what is DNA
-coded infomation put together to make an organism work
what does DNA determine
and where is it found
what inhertied characteristics you have
-found in the nucleus of animal and plant cells, in long strutctrues called chrosomes
what is DNA
-a polymer and is made up of 2strands coiled together in the shape of a double helix
what does a gene code for
a specific protein
-codes for a particular sequence of amino acids that are put together to make specific proteins
-only 20 amino acids are used, but they make up thousands of proteins
what’s a genome
an organism everyone has
-(entire set of genetic material)
state the 2ways reproduction happens
-sexual
-asexual
what is sexual reproduction
-where genetic material from 2organisms a mother and father combined to produce offspring
what happens in sexual repoduction
-mother and father produce gametes by meosis
-e.g egg and sperm cells
-each gamete contains 23chromosomes
-the egg and sperm cell fuse together (fertilisation) to form a cell with the full number of chromosomes
define sexual repoduction
involves the fusion of male and female gametes, because there are 2parents, the offspring contain a mizture of their parents genes
state why offspring inherits features from both parents
-as it inherits features from both parents and recieves a mixture of chromosomes from mum and dad
state the difference between sexual reproduction and asexual
-sexual produces genetically different cells whereas asexual produces genetically identical ones
-asexual involves the use of one parent
-sexual is by meiosis but asexual is mitosis
asexual reproduction characteristics
-1parent so offsprings genetically identical to the parent
-happens by mitosis
-bacteria, plants and animals reproduce asexually
define asexual reproduction
-theres only 1parent and no fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring.
-offspring are genetically identical to the parent and they’re clones
what are gametes produced by
meiosis
-they only have 1copy of each chromosomes so when gamete fusion takes place, you get the right amount of chromosomes again
explain the process of meosis
half the normal number of chromosomes
-before the cell divides, it duplictes its genetic infomation and forms 2 armed chromosomes
-after replication the chromosomes arrange themselves into pairs
-in 1st line division the chromosome pairs line up in the centre
-pairs are then pulled apart so each cell has a copy of each chromosome
what happens in the 2nd division
chromosomes line up again in the centre of the cell
-the arms of chromosomes are pulled apart
state what happens to the cell produced by gamete fusion
-they replicate itself
-after theyve fused the new cell divides by mitosis to make a copy of itself
-mitosis repeats many times to produce lots of new cells in an embryo
-as embryo develops they then differentiate into new types of a specialised cell, making up a whole organism
state what chromosome males have
XY
- Y causes male characteristics
state what chromosome females have
XX
the XX combination allows female characteristics to develop
what diagram do you draw to show the probability of having a boy or girl
-a Punnett square
(genetic diagram)
what are alleles
-all genes that exist in different versions
-represented by letters
what has to happen for an organism to be homozygous
if an organism has 2 alleles for particular genes that are the same
what has to happen for an organism to be heterozygous
if 2alleles are different
-only 1 determines what characteristic is present
-the characterisitic shown is the dominant allele (use captial leter)
-other is recessive
why do organisms display recessive characteristics
-both alleles are recessive
e.g cc
why do organisms display dominant characteristics
as the dominant allele overrules the recessive one could be CC OR Cc
what are genotypes and phenotypes
-combination of alleles
-characteristic you have e.g brown eyes
genetic dirarams
what is cystic fibrosis
-a genetic disorder of the cell membrane
-it results in the body producing thick sticky mucus in the air passages and in the pancreas
-caused by a recessive allele
state a genetic disorder caused by a dominant allele
-polydactyly
where a babys born with extra fingers or toes
-can be inherited if 1parent carries the defective allele
state arguments against embryonic screening
-screenings expensive
-may come a point where everyone wants to screen their embryos so that they can pick the most desireable one
E.G WANT ONE WITH BLUE EYES OR BLOND HAIR
stage arguments for embryonic screening
-helps stop people suffering
-treating disorders costs the government a lot of money
-laws to stop it going too far
what is variation
differneces that exist between individuals
what are mutation
-changes to the genome
-its a rare change in an organisms DNA that can be inherited
-means the genes altered
-
state charles darwins theory
-only the fittest survive
-organisms with most suitable characteristics for environment are successful competitors and would be more likely to survive
-then reproduce and pass on genes for characteristics successful to their offspring
what is the theory of evolution
-that all of todays species have evolved from simple life forms that firdt started to develop over 3billion years ago
state 3 reasons why species become extinct
- environment changes too quickly
- a new predator kills them all
- a new disease kills them all
what is selective breeding
when humans artifically select plants or animals that are going to breed so that they remain in populations
examples of organisms that are selectively bred
-animals that produce more meat or milk
-crops with disease resistance
-decorative plants with big or unsual flowers
state the basic processes involved in selective breeding
-selecting 1 with characteristics your after
-breed them with each other
-best of offpsring + breed together
-continue process over several generations and the desirable trait gets stronger
main problem with selective breeding
-it reduces the gene pool
(the number of different alleles)
-inbreeding causes health problems
what is genetic engineering
-to transfer a gene responsible for a desirable characteristic from 1 organisms genome into another organism
pros of gm crops
-increases the yield
-already being grown in some places without any problems
cons of gm crops
-affects number of wild flowers
-not convinced there safe
-transplanted genes may get out into natural environment
state how fossil fuels are formed
- gradual replacement by minerals
- casts and impressions
- preservation, places where no decay happens
state the 3 domain system
- archaea
- bacteria
- eukaryota
