Inherited Change Flashcards
describe the composition of chromosomes in human body
22 homologous chromosomes/autosomes
one sex chromosome (XX= female/XY= male)
definition of inheritance
transmission of genetic information from generation to generation
definition of chromosome
thread like structure of DNA containing genes
definition of haploid cell
one complete set of chromosomes (n=23 chromosome)
definition of diploid cell
two complete sets of chromosomes (2n = 46)
definition of meiosis
reduction division resulting in four daughter haploid cells
describe independant assortment
different chromosomes combination and chromosomes line up randomly by equator
describe meiosis I
prophase: chromosomes become visible condensation nuclear envelope disappears centrioles migrate to opposite poles; spindle forms; bivalents form; chiastmata formation; metaphase: bivalent line across the equator spindle attach to centromere anaphase: whole chromosomes pulled by microtubules to opposite poles telophase: nuclear envelope reforming nucleolus reforming cytokinesis two cell containing 23 chromosomes
when do centrioles replicate and move to poles + chromosomes condense
early prophase
when do homologous chromosomes pair up to form bivalents
middle prophase
describe meiosis II
same process as normal meiosis (no bivalent forming bcos already there)
BUT
anaphase = centromeres divide and pull chromatids to opposite poles
form four haploid cells
describe spermatogenesis
diploid cells divide by mitosis
spermatogonia - primary spermatocytes - + meiosis I - secondary spermatocytes (haploid) - + meiosis II - spermatids - spermatozoa
describe oogensis
diploid cells divide by mitosis
oogonia - (stop prophase I) - primary oocytes - continue to end of meiosis I - two haploid cells - secondary oocyte/one polar body - secondary oocyte released per month
how is a zygote formed
ovum + spermatozoan
which are the male parts in plants
anther
filament
which are the female parts in plants
stigma
style
ovary
describe formation of male gametes
pollen mother cells divide by meiosis to form 4 haploid cells;
each divide by mitosis to form 4 haploid cells with two nucleus;
mature into pollen grains;
generative + tube nucleus
describe formation of female gamete
spore mother cell divide by meiosis to form 4 haploid cells
three degenerates - one haploid devleops into embryo sac
sac grows - haploid nucleus divide by mitosis 3 times to form 8 - one nuclei becomes female gamete
definition of fertilisation in plant
pollen grain male gamete fuses with female gamete in ovule
definition of genotype
alleles possessed by an organism
definition of homozygous
having two identical alleles of a gene
definition of heterozygous
having two different alleles of a gene
definition of phenotype
observable characteristics resulting from genotype and environment
definition of dominant
phenotype of allele is expressed both in hetero/homo zygous
definition of recessive
phenotype of allele only expressed when dominant allele is not present
definition of codominant
more than or two phenotypes possible;
phenotype of heterozygote different from homozygous;
definition of F1 generation
offspring resulting from cross between homo-dom + homo-recc
definition of F2 generation
offspring resulting from cross between two F1 organisms
definition of autosomal linkage
when one or two more genes on same chromosome tends to be inherited together and are on autosomes
describe how sickle cell anemia is caused
mutation of base substitution from
glutamic acid to valine
describe the link between sickle cell anemia and malaria (5)
sickle cell cannot carry O2 well; homozygous HS die; heterozygous has trait + less likely to suffer from malaria; malaria is lethal; selective advantage;
example of sex linked gene
haemophilia - blood fails to clot
gene used for blood clotting
factor VIII
why are males more likely to have haemophilia
females have XX so it needs both chromosomes
ratio of dihybrid crosses with (het/homo) + (het/het)
1: 1:1:1 = heterozygous crossed with homozygous recessive
9: 3:3:1 = heterozygous crossed with heterozygous
how can you tell the test cross is autosomal linkage
NOT 9:3:3:1/1:1:1:1 ratio;
large number of parental phenotype;
no independant assortment;
what does COV value show
probability of genes being independanly assorted = high value - large distance = more likely to split
describe mutation
random change in base sequence of DNA
examples of mutations
albinism (homo rec)
huntington’s (dom)
describe the cause of albinism
dark pigment melanin missing
no tyrosinase
describe the cause of huntington’s disease
neurological disorder = mental+ physical deterioation
repeated triplet bases of CAG
definition of structural genes
structural protein;
enzyme/tRNA;
needed for structure in cell;
definition of regulatory genes (5)
control gene expression; codes for transcription factor; binds to promoter; stops/allows binding of RNA polymerase; examples: lac repressor;
definition of constitutive genes
makes protein all the time
definition of facultive genes
only transcribed when needed
definition of repressible enzymes
synthesis of repressible enzymes inhibited by binding repressor protein on specific site
definition of inducible enzymes
synthesis only occurs when substrate is present
describe the diagram of lac operon
reg gene - promoter - operator - Z - Y - A
what is lacZ
B galactosidase (lactose into glucose and galactose)
what is lacY
permease (increase permeability for lactose)
what is lacA
transcetylcase (transfer acetyl group from CoA to galactose)
describe gene control when no lactose is present
NO TRANSCRIPTION
Regulatory gene codes for repressor protein
Repressor binds to operator (part of DNA)
RNA polymerase cannot move and bind to promoter
No transcription of three structural genes
how do we remember the lac operon
I Poop On Zebras You Ass
describe gene control when lactose is present
TRANSCRIPTION
Lactose taken up by bacterium
Lactose binds to repressor protein
Repressor protein is allosteric
Shape is distorted and prevents binding to DNA
RNA polymerase can pass and transcribe three structural genes
why do we need to switch on/off production of enzymes
proteins in excess;
waste of amino acids;
decrease growth
describe gene control in eukaroytes
transcription factors bind to promoter region;
TF binds to DNA;
binds to RNA polymerase;
allows transcription;
what do transcription factors determine
sex in mammals;
responses to environmental stimuli;
allowing hormones to take effect;
where does the repressor bind on (DNA)
operator
where does the RNA polymerase bind to
promoter
describe the plant hormone gibberilin controlling seed germination (6)
DELLA protein bound to PIF (transcription factor)
PIF cannot bond to gene promoter
Gibberillin bonds with receptor and enzyme
Initiates destruction of DELLA protein
PIF binds to promoter and transcription is initiated
Stimulating synthesis of amylase by mRNA coding for amylase
definition of locus
position of gene on chromosome
