Genetics S25-CH15-17

how many bases in mRNA codes for an amino acid?

Three bases in mRNA code for one amino acid.

what is a mutation?

A mutation is a change in the DNA sequence that can affect gene function and may lead to different traits or diseases.

what is a mutant

A mutant is an organism or cell that has undergone a mutation, affecting their phenotype

point mutation

one nucleotide change in mRNA

transposable elements

DNA sequences that can change their position within the genome, potentially disrupting genes and affecting gene expression.

forward allele change

wild type to mutant allele

reversion allele change

the change of a mutant allele back to the wild type allele.

random mutations

spontaneous changes in the DNA sequence that occur without any specific cause, leading to genetic variation.

auxotroph

mutant organism

prototroph

wild type organism

spontaneous mutation

a random change in the DNA sequence that occurs without an external influence, contributing to genetic diversity.

induced mutation and examples

cause by external factors like known mutagens- chemicals, UV, radiation

germline mutation

germ line cells that transmit mutations, through gametes

somatic mutations

mutations that occur in non-germline cells and are not passed to offspring, often affecting individual cells in the body.

transition mutations

pyrimidine exchanges with another pyrmidine or purine exchanges with another purine.

transversion

mutation where a purine is substituted for a pyrimidine or vice versa.

isoalleles

different alleles at the same locus that are basically the same and code for the same protein, but can change the DNA sequence

silent mutation

A mutation that does not result in a change in the amino acid sequence of a protein.

missense mutation

A mutation that results in the substitution of one amino acid for another in the protein sequence.

conservative missense mutation

A type of missense mutation where the substituted amino acid has similar properties to the original, often resulting in minimal effect on protein function.

nonconservative missense mutation

A type of missense mutation where the substituted amino acid has different properties from the original, often resulting in a significant change in protein function.

nonsense mutation

A mutation that introduces a premature stop codon in the protein-coding sequence, leading to truncated and usually nonfunctional proteins.

null functional protein

A protein that has lost all functionality due to mutations or deletions, often resulting in a complete absence of the protein's normal action.

underactive functional protein

A protein that exhibits reduced functionality compared to the normal, often due to mutations that impair its activity but do not eliminate it completely.

overactive functional protein

A protein that exhibits increased functionality or activity compared to the normal, often due to specific mutations that enhance its performance.

gain of function functional protein

A type of protein that results from mutations leading to enhanced or novel activities, providing a gain of function that was not present in the wild-type version.

conditional auxotroph

A microorganism that requires certain growth factors or nutrients that it cannot synthesize on its own, but can grow without them under specific conditions.

temp sensitive organism

An organism that can grow and reproduce under certain temperatures but requires specific conditions to survive at non-permissive temperatures.

suppressor sensitive organism

An organism that exhibits a phenotype reversing the effects of a specific mutation when a suppressor mutation is present. two mutations-good one fixes the bad one

homologous repair steps

The process of repairing double-strand breaks in DNA through a mechanism that uses a homologous sequence as a template. exonuclease degrades 5’ ends, recombination proteins help align the homologous sequences, and DNA polymerase synthesizes new DNA. Finally, ligase seals the repaired strand.

exonucleases

are enzymes that remove nucleotides from the ends of DNA or RNA molecules, playing a crucial role in DNA repair and processing.

deamination

is a chemical reaction that removes an amine group from a molecule, often leading to point mutations in DNA by converting cytosine to uracil.

frameshifts

occur when nucleotides are inserted or deleted from the DNA sequence, altering the reading frame of the codons and potentially leading to significant changes in protein structure.

chromosomal rearrangements

are changes in the structure of chromosomes, which can involve duplications, deletions, inversions, or translocations of chromosome segments, often leading to genetic disorders or cancer.

polymerase slipping

during DNA replication, DNA may breathe and open a bubble that allows the DNA polymerase to slip, resulting in the addition or deletion of repeating sequences, which can cause frameshift mutations.

electromagnetive spectrum

x rays induce mutations through ionization which breaks DNA and UV light excites electrons, causing T dimers and other forms of DNA damage.

how to fix ionizing radiation

photolyase binds to the created T dimer, cleaves cross links and restores the correct DNA sequence.

excision repair of DNA

DNA repair endonuclease recognizes, binds and frees damaged bases, DNA pol fills the gap using comp. DNA strand, ligase seals off DNA pol break.

base excision repair

when something like deamination of C occurs turning it to a U, DNA glycolyase removes the uracil, and DNA polymerase and ligase restore the correct base.

nucleotide excision repair

when a t dimer occurs, endonuclease makes 5’+3” cuts, helicase releases it, DNA pol fills the gap and ligase seals it

mismatch error in E.Coli

fixes errors after replication, but when it fails, the parental strand is methylated to distinguish it from the daughter strand, which is not yet methylated. This system recognizes the mismatched bases and excises them for repair.

polyploidy

scale of how many sets of chromosomes you have

aneuploidy

the condition of having an abnormal number of chromosomes, either more or fewer than the typical diploid number.

monosomy aneuploidy

2n-1 of chromosomes

trisomy aneuploidy

2n+1 of chromosomes

nondisjunction

failure of chromatids to seperate during meisosis, causing an abnormal distribution of chromosomes in daughter cells.

down syndrome

a genetic disorder caused by trisomy of chromosome 21.

patan syndrome

a genetic disorder caused by trisomy of chromosome 13, leading to physical deformities and intellectual disability.

edward syndrome

a genetic disorder caused by trisomy of chromosome 18, resulting in severe developmental delays and various physical abnormalities.

turner syndrome

a genetic condition resulting from the absence of one X chromosome in females, leading to developmental issues and infertility.

amniocenter

a medical procedure used to obtain amniotic fluid for prenatal testing, which can provide information about genetic disorders and fetal health.

monosomic

referring to a condition in which an individual has only one copy of a particular chromosome instead of the usual two, often resulting in genetic disorders.

turner syndrome somatic mosaic

a form of Turner syndrome where some cells have the typical two X chromosomes, while others have only one, leading to varying degrees of symptoms and features.

drosophila gynandromorphs

(xx/xo) mosaics where some cells think they’re female and some male

chromosome deletion

missing chromosome segment

chromosome duplication

an extra copy of a chromosome segment

chromosome inversion

a segment of a chromosome is reversed end to end.

pericentric chromosome inversion

including centromere

paracentric chromosome inversion

a chromosome segment is inverted but does not include the centromere.

oncogene

a mutated gene that promotes uncontrolled cell division and cancer.

chromosome translocation

a genetic alteration where a segment of DNA is moved from one chromosome to another, often leading to cancer.

reciprocal chromosome translocation

a type of chromosome translocation where segments from two different chromosomes are exchanged.

compound chromosomes

Chromosomes formed when two or more chromosomes fuse together, often observed in certain types of cancer.

robertsonian chromosomes

two different chromosomes at a centromere