topic B6 - inheritance Flashcards
define chromosome
a structure found in the nucleus which is made up a long strand of DNA
define gene
a small section of the DNA which codes a particular sequence of amino acids to form a specific protein
DNA
a long thread of genetic material that forms a double helix
genome
is the entire genetic material of that organism
alleles
different forms of the genes
clones
an organism that is genetically identical
phenotype
the physical characteristic
genotype
genotype is a combination of alleles of an organism inherits from its parents - the genetic makeup of an individual
heterozygous
give examples
different alleles are present
Bb
homozygous
example
when both alleles are the same
bb
BB
gamete
a sex cell with half a set of chromosome of the parent
mitosis
one cell is copied into 2 identical cell
dominant alleles are represented
example
capital letters
BB
if the alleles are dominant
the phenotype is the allele that is dominant
recessive allele
are represented by lower case
how many copies of recessive alleles
2 copied are needed or no dominant allele
cystic fibrosis
is a disorder of the cell membrane resulting in thick mucus in the airways and the pancreas
key points of cystic fibrosis
controlled by single gene
caused by a recessive allele
in order to have cystic fibrosis
both parents need to either be carriers - have one recessive allele each
or
one parent must have 2 copies of the recessive allele
what sort of people won’t have cystic fibrosis
a person with one recessive allele and one normal allele does not have cf but are carriers
polydactyly
having an extra finger/toes
what causes polydactyly
dominant allele
why can’t you be a carrier for polydactyl
because the dominant allele will have that characteristic
female gene
XX
male gene
XY
reproductive organs
testes and ovary
what is embryo screening
when embryo is screened / checked for genetic disorders
stages of embryo screening
during IVF embryo are fertilised in a laboratory
then one cell from each embryo is removed and gene is tested to see if it has the genetic disorder and it is then implanted back into the mothers womb
arguments against embryonic screening
embryo screening is very expensive and some may think that money should be spent elsewhere in the healthcare
could encourage to pick a desirable characteristic (creating designer baby )
people may find this unethical
the procedure can lead to miscarriages
may promote prejudice as it suggests that those with genetic disorders will not live a full life or might be discriminated
an increase in abortion
arguments for embryo screening
maybe able to correct family alleles
be able to treat inherited disorders
reduce the number of suffering
there is a regulation in pace to stop it from getting out of control
sexual reproduction
sexual reproduction occurs in meiosis to form 4 non-identical cells called gametes . it involves the fusion of a male and female gamete . the cell divides twice and each gamete - half the set of chromosomes haploid ,
the genetic information from each parent is mixed , producing a variation in the offspring .for example of sexual reproduction is sperm cell fusing with the egg cell
asexual reproduction
asexual reproduction occurs in mitosis so one cell is copied into 2 genetically identical cells. it has a full set of chromosome - diploid and because there is no mixing of of genetic information so the offspring can form clones.
asexual reproduction occurs in
mitosis
sexual reproduction occurs in
meiosis
asexual forms
2 genetically identical cells
sexual forms
4 non-identical cells called gametes
asexual chromosome
diploid - full set of chromosome
sexual reproduction
haploid - half set
the offspring of asexual reproduction
genetically identical and can form clones
the offspring of sexual reproduction
produces variations in the offspring
stages in meiosis
in the first stage of meiosis, the cell makes copies of chromosome
the cell divides into 2 - each with half the amount of chromosome 46
then it divides again producing 4 cells - 23 chromosome
these cells are called gametes and are all genetically non-identical from each other
fertilisation
the male gamete - containing 23 chromosome and the female gamete also containing 23 chromosome fuse at fertilisation to produce a cell with 46 chromosome
what happened after fertilisation
the cell divides by mitosis to produce a clump of identical cells
more and more cells are produced forming an embryo
as the embryo develops the cell begins to differentiate into different types of cells
DNA
is a polymer made up of 2 strands that twist around to form a double helix ( this increases the surface area )
understanding the human genome enabled us
- Search for genes linked with different types of diseases
- improve understanding and treat inherited disorders
- help trace the human migration pattern
meiosis
a cell division in which the number of chromosome is halved and takes place in the reproductive organs eg testes an ovary
why is meiosis important
it involves the fusion ( the process is known as fertilisation ) of the male and female gamete both containing half the number of chromosome (23) to produce offspring with the full number of chromosomes (46) this takes place in sexual reproduction
