3b, inheritence Flashcards
define genome
the entire DNA of an organsim
define gene
section of a molecule of DNA that codes for a specific protein
what does the nucleus of the cell contain
chromosomes, where DNA and genes are located
describe the structure of a DNA molecule
- double stranded
- double helix
- sugar phosphate backbone
- two bacbones held together by nitrogenous bases
-4 bases with complimetary base pairings (ATCG)
- nitrogneous bases hld by hydrogen bonds
4 DNA bases + rule
AT
CG
inheritance and chromosomes link?
characteristics are passed down via chromosomes that offspring inherit from parents
where chromosomes unraveled = dna
what does DNA stand for
DeoxyriboNuceluic Acid
chromosome structure
each chromosome contains one double-dtranded DNA molecule.
it is supercoiled around prteins called histones.
what are alleles
different version of genes
what is DNA made up of?
nucleotides
what is the composition of nuceluotides?
- phosphate
- (deoxyribose) sugar
= backbone - nitrogenous base (ATGC)
hwo are nucleotides arranged?
- anti-parallel
- complimentary base pairings
- hydrogen bonds
4 scientists that dsicovered DNA
- James Watsons
- Francis Crick
- Rosalind Franklin
- Maurice Wilkins
what is the need for dna replication?
- order of bases = genetic code
- to pass this on, genetic code needs to be replicated
- occurs just before mitosis
what method for dna replication? and why
semi-conservative
bc..
each new DNA molecule has a ‘parent’ (old) bacbone, and a new backbone from the free nucleotides.
steps for dna replication (5stepsintotal)
- unwind
- unzip
- free nucleotides
- join
- rewind
step 1 of dna replication?
unwind
DNA unwinds from double helix –> ladder
step 2 of dna replication?
unzipped
enzyme DNA helicase breaks hydrogen bonds between bases, unzipping DNA into 2 strands
step 3 of dna replication?
free nucleotides
free-lying nucleodtides within the nucleus bind the the complimentary base of each strand.
each strand acts as the template
due to the complimentary base pair rule, the genetic code won’t change as each base attratcs the free nucleotide tot heir own pair.
step 4 of dna replication?
join
enzyme DNA polymerase catalyses the synthesis of new DNA strands, and joins the strands together, to form a new DNA molecule.
step 5 of dna replication?
rewind
replication finished
2 pairs of DNA produced b4 mitosis due to 2 daughter cell copies
protein synthesis and gene link?
each gene codes for a specific protein.
1 gene = 1 protein
2 steps of protein sythesis?
- transcription
- translation
protein sythesis- transcription?
- DNA stays in the nucleosu (doesnt move out).
- code first copied copied onto messanger RNA (mRNA)
- RNA polymerase binds to gene and brinsg complimentary base pairings.
- mRNA molecules small enough to pass through nucleus into cytoplasm for next stage.
differences in RNA structure vs DNA structure
- AUGC, no thymine, instead, uracil.
- Single stranded
- shorter molecule length
RNA sugar = ribose
DNA sugar = deoxyribose
protein synthesis - translation
- mRNA binds to ribosomes
- ribosome reads base 3 at a time = codon.
- transfer, tRNA, contains anti-codon, which is 3 complimentary bases that macth the codon at the mRNA.
tRNA brings the AA to the ribosomes to make the proteins.
- mRNA moves along ribosome, tRNA enters and reads codon, using anti-codon.
- generates specific AA depending on code read (anti-codon)
- process repeates, and peptide bond forms along AAs.
process continued until stop codon reached and read.
protein = polypeptide chain = formed and now folded into 3d shape.
how many chromosomes do humans have?
46, 23 pairs
what is known as teh karyotype for humans?
a picture of all the chromosomes in a cell
what does a homologous pair mean?
chromosomes come in a homologous pair, which means tehy contain the same type of genes that code for the same characeristics, but may contsin different alleles.
phenotype?
observable characteristic that is expressed by a cell
hwo is a phenotype decided?
whih allele is dominant vs recessive.
dominant?
- almost always expressed in cells’ phenotype.
- only one copy of allele needed needs tp be inherited to be expressed.
- UPPERCASE
recessive?
- only expressed if 2 copies present
- if only 1 copy present, effect ‘masked’ by dominant allele.
- LOWERCASE
genotype?
combo of alleles that a person has that codes for their phenotype.
heterozygous?
homologous pair with different alleles
homozygous?
homologous pair with same alleles
whwich feautrues tend to be recessive?
lighter feauturess?
decribe the following genotypes:
where B = brown eyes, and b = blue eyes
- Bb
- BB
- bb
- homologous pair, heterozygous, dominant for brown eyes
- homologous pair, homozygous dominant for brown eyes
- homologous pair, homozygous, recessive for blue eyes.
co-dominance?
where sometimes, both alleles contribute to the phenotype.
examplies of co-dominance?
- blood groups
- flower colours
how is gender determined through chromosomes?
determined by whole chromosomes
XX = female
XY = male
- all females have 2X chromosomes, and can only pass on the X chromosome through their eggs.
- all males have an X or Y chromosome, and they can eitehr pass an X OR Y through their sperm
chromosomes dependednt on chance of gametes, depends on which sperm meets + penetrates egg (50/50)
polygenic inheritence?
- where many characteristics are controlled by 2 or more genes working together.
- skin colour , height, weight
what is pedigree analysis?
- used to shwo the chance of genetic disorders inherited within generations
what is a carrier within pedigree analsysis?
they carry a copy of the ‘faulty’ allele in their genotype but aren’t affected by said disease.
variation
where caharcetrsitcs are controlled by genes and environment. (nature vs nurture)
- environemtnal chnages to phenotype cannot be inherited/passed on.
- environmental changes havea larger impact on plants (water, sunlight, minerals, temp)
mutation
rare random chnage in DNA
can be passed onto next gen
can create a new allele, but most have 0 real effect
= chnage in sequence of bases
= chnange in genetic code
= chnage in protien
= change in characteristic of phenotype
enzyme effect on mutation.
- mutation causes chnages in AAs and protein shape
- enzymes are made up of proteins,
- there4, enzyme f(x) can be altered, and stop production all 2gether.
most mutations dont cause harm bc.//
- new codom might code for same AA
- can be recessive, masked by dominant
- muatuion in a minor part of DNA
muattions cause..
VARIATION
mutations can cause…
cancer
mutations cuased where and effects
- in a body cell, they can die, and NOT passed on.
- in gamete, can be passed on.
since mutations are a random change, their chance can be increased.
- ionising radiation (UV and XRAYS)
- chemicals called mutants (cigg. smoke)
theory of evolution basic?
all orgs have evolved from simple lifeforms.
natural selection? theory bases ( what does it cause…)
explians the theory of evoution, caused it.
what is natural selection
- all from a common ancestor
- some would have undergone mutation
- orgs that were better suited for the environment, would have survived and reproduced.
- they porduce more offspring with similar characteristics
- others would die.
= natural selection
= survival of the fittest
what is anitbitoic resistence
- antibitoics drugs that can kill basterial pathogens, arent effective anymore bcs the basteria has evolved.
what is antibitoic resistence an example of?
fast evolution.
normla evol = slow, but bc bacteria produce very fast (asexual), its fast, and they prodicye superbugs.
antibiotic resistence process?
- there is a natural population of bacteria (variation incl.)
- a chnace in mutation can lead to bacteria becoming less resistent to drugs.
- ther4, it survives and others die.
- bc, bacteria reporduce fastly, population can grow rapidly
- bacteria asexcually, so all offspirng inherit resistent allele.
- bacteria have evolved due to natural selection.
what is one thing we can decduce about the bases due to the complimetary base rule?
in each molecule of DNA,
amnts of A = amnts of T
amnts of C = amnts of G
why might a genetic mutation might not affect the phenotype of an organism
- code for same AA
- no change in enzyme/substrate still fits
- may not affect enzyme 3D bonding structure
- mutation is recessive, effect is masked
- non-coding DNA
