Patterns of Inheritance 6.1.2 module 6 Flashcards
what is continuous variation
value within a range/quantitative
eg) height, length of stalk
-genetic and environmental factors
-polygenic controlled by a number of genes
no limit on value, 2 extremes
can be shown through standard deviation curve
what is discontinuous variation
distinct catagories
-qualitative
-eg) blood group, hair colour, wrinkle or smooth peas
-mongenic/controlled by one or two genes
limited number of phenotypes
no in between catagories
can be shown in bar chart
what is an allele
a different form of the same gene
what is a phenotype
characteristics displayed by an organism
what is a genotype
the alleles an organism has eg) Bb BB bb
what is a dominant allele
will always be expressed if present in genotype
what is a recessive allele
expressed if two copies are present
what are homozygous alleles
same alleles identical alleles for a gene can be dominant or recessive
what are heterozygous alleles
different alleles present in the zygote
what is the locus
position of a gene on each homologous chromosome
what are homologous chromosomes
chromosomes w/ same structure features and patterns of genes
what are Epigenetics
(means above genetics) the idea that both nature and nurture affect how an organism looks and acts
eg) rats mums and illnesses such as diabetes
both influenced by genes or lifestyle, look of leaf, obesity
how can genes and environement effect leaf appearance
genes code for chlorophyll in normal genome
-environment has determined leaf appearance (physiology causes a change in phenotype)
how can the environment effect the leaf appearance
Chlorosis- mineral deficiencies
- lack of Fe- cofactor for enzymes in chlorphyll production
- lack of Mg- (Mg is in chlorophyll) chlorophyll can’t be synthesised
also Virus infections which interfere w/ metabolism of chlorphyll production and leaves tissues turn yellow
Etiolation- lack of light- plants turn off chlorphyll production to conserve resources, plants grow abnormally long and spindly due to not enough light.
arguments that obesity is caused by genes example
- ‘ob’ gene codes for secreted protein that may function in cell signalling pathway of adipose tissue so more fat deposits
- ‘LEP’ gene codes for hormone leptin which is produced by fat cells in proportion to their size eg) bigger cells=more leptin (hormone associated w/ satiety)
arguments that obesity is caused by environment example
- inbalanced calories uptake and use
- availability of food
- diet choice
what is a phenotype
characteristics displayed by an organism
what is a genotype
the alleles an organism has eg. BB bb Bb
what is a dominant allele
always expressed if present in genotype
what is a recessive alleles
expressed if two copies are present
what does homozygous mean
same alleles for gene eg BB or bb either recessive or dominant
what does heteorozygous mean
different alleles are present in the zygote
what is the locus
position of a gene on each homologous chromosome
what are homologous chromosomes
chromosomes w/ same structural features and patterns of genes
what is epigenetics
In biology, epigenetics is the study of heritable phenotype changes that do not involve alterations in the DNA sequence.
idea of ‘nature vs nurture’
example being the rats mum and level of licking being down to nurture. But those that were licked less still had the methyl group attached which switched off the gene for licking. the methyl group is orgionally attached in all rat babies
what is the enzyme used in transcription
what are the names of the strands of dna
rna polymerase - synthesising strand of mRNA
the coding/ sense strand 5’ to 3’
and the antisense/ template strand 3’ to 5’
where does transcription occur
nucleus
where does translation occur
ribosomes in cytoplasm
which types of RNA are involved in translation
mRNA
tRNA
rRNA
what does the tRNA have on it
anticodon complementary to codon which syntheisises an amino acid forming a polypeptide chain
look at 10/01/20 if dont understand
order of a protein forming?
which enzymes involved
DNA replication- DNA polymerase involved forms DNA
Transcription- RNA polymerase involved forms mRNA
Translation- at the ribosome froms polypeptide/protein
what is a degenerate code in terms of genetic codes
idea that more than one codon can code for amino acid! describes why silent mutations have no effect on phenotype
only 20 amino acids to code for but 64 cobinations of codons (4^3) so some code for same.
what is meant by a non-overlapping code
Starts with AUG and ends with a stop codon and is read in 5’ to 3’ direction ensuring it is non-overlapping
adjacent codons don’t overlap and no base can take part in formation of more than one codon.
what is meant by universal code
DNA is universal as all living organisms have genes made up of DNA
what is a mutation
a change in the base sequence of DNA in cell division and copying which changes the arrangement of genes (structure of chromosome)
how is albinism caused
enzyme involved in chemical pathway is effected so doesnt have correct active site and can’t catalyse the reaction pathway leading to the formation of melanin. This stops production of enzyme for this and cells cant produce melanin
what type of nucleic acid holds together the bases i translation
mRNA
what effect do stop codons have
ensure DNA is non overlapping
they dont code for an amino acid
aka nonsense or termination codons
what name would be given to a mutation that changes UUU to UUC
substitution
what are the 4 types of point mutations
substitution ATG»_space; ACG
insertion ATG»_space; ATCG G becomes part of next codon
deletion ATG»_space; AG
inversion ATG»_space; AGT
which point mutations cause a frameshift and what does that mean
insertion and deletion
the addition or removal of a base alters the reading frame of a gene. It can change every codon after the mutation and can dramatically change the amino acid sequence
if the base substitution is silent what does this mean
DNA sequence has changed but codon hasnt because the DNA code is degenerate
dont change phenotype and most mutations are this type»_space;>neutral
what is a missence base substitution mutation
DNA change single nucleotide change results in a codon that codes for a different amino acid (alters
this can have large effects such as sickle cell which is caused by base substitution
what is a nonsense base substitution mutation
every amino acid coded for after that codon (stop codon) won’t be copied which can cause things like cystic fibrosis if chain stops early
what is cystic fibrosis catagorised as
severe repiritory problems
inadequate pancreatic function caused by accumulation of sticky mucus
this is due to mutation in CFTR coding gene which means it the final protein can’t allow Cl- ions across cell membranes
what kind of point mutation is cystic fibrosis usually caused by
deletion
nonsense
how does a framshift effect the resulted protein/ polypeptide chain
completely inactive/ useless due to reading in translation
examples of useful/beneficial mutations
> ability to digest lactose-spontaneous mutation but not in many mammals who develop intolerance after suckling
bacterial resistance by natural selection
rat poison resistance
camouflaging shell colours and banding on snails
examples of detrimental mutation
> sickle cell anemia
albinism
cystic fibrosis
huntingtons
how can sickle cell anemia be beneficial?
in areas where malaria is present, the parasite/plasmodium can only live in normal red blood cells so anyone heterozygous for sickle cell won’t suffer from malaria.
how is sickle cell caused
base substitution mutation to mRNA base sequence in transcription and changes the polypeptide is haemoglobin as amino acid changes from Glu to Val
instead of globular protein a more fibrous stranded haemoglobin is formed. Hydrophobic VALine binds to other hydrophobic regions causes clumping and sickle cell shape
what are the effects of sickle cell
> insoluble haemoglobin formed can’t carry oxygen as effectively so is tired constantly
can from clots in capillaries- blocks blood supply to vital organs
sickle cells destroyed more rapidly than normal red blood cells so low red blood cell count - anemic
how can sexual reproduction lead to genetic variation within a species
meiosis and the random fusion of gametes at fertilisation
what is monogenic inheritance
the inheritance of a single gene
what is dihybrid inheritance
inheritance of two different characteristics caused by two genes which may be located on different pairs of homologous chromosomes
each of these genes can have 2 or more alleles
eg round and yellow peas ect
