BIOL 141 Spring 2025 Exam 3 Study Guide Lectures

Flashcards for BIOL 141 Exam 3 Review

Mitosis

Cell division resulting in two identical daughter cells.

Prophase

First stage of mitosis, chromosomes condense and become visible.

Metaphase

Chromosomes align along the metaphase plate.

Anaphase

Sister chromatids separate and move to opposite poles.

Telophase

Chromosomes arrive at the poles, and nuclear envelope reforms.

Interphase

The period of the cell cycle between cell divisions.

G1 phase

Cell grows and duplicates organelles.

S phase

DNA replication occurs.

G2 phase

Cell prepares for division.

Cytokinesis

Division of the cytoplasm to form two separate cells.

Karyotype

Visual representation of chromosomes.

Autosomal chromosome

Non-sex chromosome (1-22 in humans).

Homologous chromosome

Members of a chromosome pair, one from each parent.

Haploid

n (number of chromosomes in a gamete).

Diploid

2n (number of chromosomes in a somatic cell).

Somatic cell

Body cell.

Gamete

Sex cell (sperm or egg).

Daughter cell

Clone of mother cell produced by cell division.

Sister chromatid

Identical copies of a chromosome created during S phase.

Meiosis

Cell division that produces gametes (sex cells).

Crossing over

Exchange of genetic material between homologous chromosomes during prophase I of meiosis.

Independent assortment

Random alignment of homologous pairs during metaphase I of meiosis.

Nondisjunction

Failure of chromosomes to separate properly during anaphase I or II of meiosis.

Monosomy

Condition where there is one less chromosome than normal (n-1).

Trisomy

Condition where there is one extra chromosome than normal (1+n).

Down syndrome

Trisomy 21.

Turner syndrome

Monosomy of X chromosome.

Patau syndrome

Trisomy 13.

Jacobs syndrome

Trisomy of Y chromosome (XYY).

Allele

Options for a gene.

Genotype

The genetic makeup of an organism.

Phenotype

Physical characteristics of an organism.

Dominant allele

Allele that is expressed when present.

Recessive allele

Allele that is not expressed when a dominant allele is present.

Homozygous dominant

Two dominant alleles (e.g., DD).

Homozygous recessive

Two recessive alleles (e.g., rr).

Heterozygous

One dominant and one recessive allele (e.g., Dr).

Incomplete dominance

No allele is completely dominant, resulting in a mixed phenotype.

Codominance

Both alleles are dominant and both are expressed.

Epistasis

One gene overrides the expression of another gene.

Polymorphism

Three or more alleles for one gene.

Quantitative trait

The trait is determined by more than one gene.

Transformation

Taking foreign DNA by a cell, changing it’s genotype.

Transcription

Copying DNA into mRNA.

Translation

From mRNA to protein (ribosome).

Codon

Three nucleotides that code for a single amino acid.

RNA polymerase

Enzyme that transcribes DNA into mRNA.

mRNA

Messenger RNA; carries the genetic code from DNA to ribosomes.

tRNA

Transfer RNA; carries amino acids to the ribosome during translation.

Ribosome

Site of protein synthesis.

Spliceosome

Removes introns from pre-mRNA.

Promoter region

Region of DNA where RNA polymerase binds to initiate transcription.

Terminator region

Region of DNA that signals the end of transcription.

Anticodon

A sequence of three nucleotides in a tRNA molecule that corresponds to a codon in mRNA.

P site, A site, E site

Sites on the ribosome where tRNA binds during translation.