Genetics Final Exam

Activators

increase the rate of transcription(positive control)

Repressors

decrease the rate of transcription(negative control)

Small effector molecules

molecules that influence transcription factor activity

inducers

molecules that increase gene expression by binding to repressors or activators

corepressors

bind to repressors enabling repressors to bind to DNA and prevent transcription

inhibitors

molecules that prevent activators from increasing transcription

inducible genes

genes turned on in response to inducers

repressible genes

genes turned off by corepressors or inhibitors

enhancer

regulate DNA sequences by increasing gene transcription(activates)

Silencer

regulate DNA sequences by decreasing gene transcription(inhibits)

attenuation

a regulatory mechanism where transcription is prematurely terminated in response to specific signals

constitutive genes

genes that are continuously expressed at a constant rate

general transcription factors

Proteins that are essential for the transcription of all protein-coding genes. They help position RNA polymerasecorrectly at the core promoter, assist in DNA unwinding, and help start transcription.

mediator

protein complex regulating RNA polymerase activity

complete dominance

one allele completely masks the effect of another. The dominant allele's trait is fully expressed, while the recessive allele has no effect on the organism's appearance when both are present

incomplete dominance

heterozygous display a phenotype intermediate between the parent phenotypes

codominance

heterozygotes simultaneously express both homozygous phenotypes without blending

overdominance

heterozygous individuals have an advantage over individuals with either homozygous genotype

somatic cells

any cell in the body that is not a reproductive cell (sperm or egg), containing two sets of chromosomes (diploid), and making uo the tissues, organs, and systems of an organism

gametes

reproductive cells that unite during fertilization to form a new organism, containing half the number of chromosomes of somatic cells

homologous chromosomes

a pair of chromosomes, one inherited form each parent, that are similar in shape, size, and genetic content, but may carry different alleles for certain traits

sister chromatid

two identical copies of a chromosome, produced by DNA replication, that are connected by a centromere and separated during cell division

crossing over

homologous chromosomes exchange genetic material between non-sister chromatids, resulting in genetic recombination and increased genetic diversity.

chiasmata

what holds the homologous chromosomes together after crossing over

synaptonemal complex

physically attaches the homologous chromosomes together

cohesion rings

protein complexes that hold sister chromatids together until anaphasee during cell division

mitotic spindle

moves chromosomes around and ensures they are evenly distributed into their offspring

synteny

when 2 or more genes are located in the same chromosome and tend to be inherited together

linked genes

genes located close together on the same chromosomes, often inherited together

X-linked genes

all female offspring of both crosses will have the same phenotype, male phenotypes will differ between the 2 crosses bc the sones will have the same phenotypes as their mothers

Test cross

cross between an F1 heterozygous and homozygous recessive

recombinant

offspring have the same combination of alleles not present in parents

non-recombinant

offspring that have same combination of alleles as one parent

kinetochore

A protein structure on the centromere of a chromosome where spindle fibers attach during cell division

kinetochore microtubule

A type of spindle microtubule that attaches to the kinetochore of a chromosome during mitosis or meiosis

polar microtubule

spindle microtubule that extends from one centrosome and overlaps with microtubules from the opposite centrosome

centromere

region of a chromosome where the two sister chromatids are held together and where the kinetochore forms

centrosome

forming the spindle apparatus during cell division

diploid

has two complete sets of chromosomes

haploid

only one complete set of chromosomes

genetic imprinting

only one allele of the gene is active, depending on whether it was inherited from the mother or the father, while the other allele is silenced (imprinted).

maternal effect

where the genotype of the mother directly influences the phenotype of her offspring, regardless of the offspring’s own genotype.

extranuclear inheritance

inheritance of genetic material outside the nucleus, usually from organelles like mitochondria or chloroplasts

sex-influenced

Traits where the expression of an allele is affected by the sex of the individual.

sex-limited

Traits that are expressed in only one sex, even though the genes for the trait are present in both sexes

reciprocal cross

A pair of genetic crosses in which the sexes of the parents are switched for a particular trait

true-breeding

self-fertilized or crossed with the same genotype, produce offspring that are genetically identical for a particular trait.

epistasis

where the allele of one gene masks or modifies the expression of alleles of another gene

gene redundancy

two or more genes perform the same or similar functions, so the loss of one gene does not produce a noticeable phenotype because another gene compensates.

complementation

two organisms with different recessive mutations in different genes produce offspring with a wild-type (normal) phenotype when crossed

intron

non-coding sequence of DNA found within a gene that is transcribed into RNA but removed during RNA splicing

exon

coding sequence in a gene that is transcribed and retained in the final mRNA after splicing

alternative splicing

during mRNA processing where different combinations of exons are joined together, allowing a single gene to produce multiple proteins

5’ cap and 3’ poly A tail

Modifications added to eukaryotic pre-mRNA during processing to protect and prepare it for translation.

template strand

DNA strand used by RNA polymerase as a guide to synthesize mRNA during transcription.

coding strand

DNA strand that is not used as a template during transcription, but whose sequence is identical to the mRNA

histone

DNA wraps around them and organize and package DNA into structural units called nucleosomes.

nucleosome

DNA packaging in eukaryotic cells, consisting of a segment of DNA wrapped around a core of histone proteins.

euchromatin

chromatin that is loosely packed and transcriptionally active, meaning genes in euchromatin are generally accessible and being expressed.

heterochromatin

chromatin that is densely packed and transcriptionally inactive, meaning genes in heterochromatin are usually silenced or not expressed.

chromatin modification

histone proteins or DNA that affect chromatin structure and regulate gene expression by altering DNA accessibility

chromatin modification

chemical alteration of DNA or histone proteins that influences chromatin structure and gene expression without changing the DNA sequence itself.

chromatin remodeling

chromatin structure is altered to regulate DNA accessibility for transcription, replication, and repair.

CpG Island

high frequency of CG dinucleotides often found near gene promoters.

transposons

DNA sequences that can move or “jump” from one location to another within the genome.

Retrotransposons

transposon that moves within the genome via an RNA intermediate. The RNA is reverse-transcribed back into DNA, which is then inserted into a new genomic location

autonomous

transposon that can move by itself because it contains all the necessary genes and enzymes

nonautonomous

cannot move by itself because it lacks the genes or enzymes necessary for transposition. It relies on enzymes produced by autonomous transposons to move.

reading frame

nucleotides in mRNA are grouped into sets of three bases for translation into amino acids.

UTR

mRNA that are not translated into protein but play important roles in regulating translation and mRNA stability

codon

three nucleotides in mRNA that corresponds to a specific amino acid or a stop signal during protein synthesis.

anticodon

three nucleotides on a tRNA molecule that is complementary to an mRNA codon.

synonymous codon

Different codons that code for the same amino acid in the genetic code. Also called “silent” codons because changes in these codons do not alter the protein sequence.

genetic code redundancy

genetic code where multiple codons can code for the same amino acid. This redundancy helps minimize the effects of mutations.

genetic code degeneracy

genetic code where multiple codons can specify the same amino acid. This provides a buffer against mutations by allowing some nucleotide changes to be silent.

Transition

point mutation where a purine is substituted for another purine (A ↔ G) or a pyrimidine is substituted for another pyrimidine (C ↔ T).

Transversion

point mutation where a purine is replaced by a pyrimidine or a pyrimidine is replaced by a purine.

missense

point mutation in DNA that results in a single amino acid change in the protein sequence by altering a codon to code for a different amino acid

nonsense

point mutation that changes a codon encoding an amino acid into a stop codon, causing premature termination of protein synthesis.

silent mutation

point mutation in DNA that changes a codon but does not change the amino acid encoded, due to the redundancy of the genetic code.

conservative mutation

missense mutation where the substituted amino acid has similar properties

frameshift

mutation caused by the insertion or deletion of nucleotides that is not in multiples of three

insertion

where one or more nucleotides are added into the DNA sequence

deletion

one or more nucleotides are removed from the DNA sequence. If the number deleted is not a multiple of three

inversion

chromosomal mutation where a segment of a chromosome breaks off, flips around (inverts), and reattaches in the opposite orientation.

inversion loop

during pairing of homologous chromosomes in meiosis when one chromosome carries an inversion.

paracentric

chromosomal inversion that does not include the centromere. The inverted segment is located on one arm of the chromosome.

pericentric

chromosomal inversion that includes the centromere, with breakpoints on both chromosome arms.

translocation

chromosomal abnormality where a segment of one chromosome breaks off and attaches to a different, non-homologous chromosome.

branch migration

process during homologous recombination where the Holliday junction moves along the DNA strands, extending the region of strand exchange between homologous chromosomes

heteroduplex DNA

double-stranded DNA molecule formed during homologous recombination where each strand comes from different homologous chromosomes, resulting in regions with mismatched bases due to sequence differences.

gene conversion

non-reciprocal genetic exchange during homologous recombination where one DNA sequence is replaced by a sequence from a homologous chromosome, often due to mismatch repair of heteroduplex DNA.

Holliday junction

cross-shaped structure that forms during homologous recombination when two double-stranded DNA molecules become connected by exchanging strands

leading strand

DNA strand that is synthesized continuously in the 5′ to 3′ direction during DNA replication, moving toward the replication fork

lagging strand

DNA strand that is synthesized discontinuously in short fragments called Okazaki fragments during DNA replication, moving away from the replication fork.

Okazaki fragments

Short DNA fragments synthesized discontinuously on the lagging strand during DNA replication.

origin of replication

specific DNA sequence where DNA replication begins. Proteins recognize this site to start unwinding the DNA and assembling the replication machinery

replication fork

Y-shaped region where the DNA double helix is unwound during replication, allowing the two strands to be copied

RNA primer

short strand of RNA synthesized by primase that provides a starting point with a free 3’-OH group for DNA polymerase to begin DNA synthesis.

telomeres

Repetitive DNA sequences at the ends of linear eukaryotic chromosomes that protect the chromosome from deterioration or fusion with neighboring chromosomes.