Comprehensive DNA, Genetics, and Evolution Review for Biology

What are the characteristics of DNA?

DNA consists of A, T, C, G; has a double helix shape; sugar is deoxyribose; has 2 antiparallel strands (5'→3'); base pairing is A-T, C-G; and it stores genetic information.

What does semiconservative mean in DNA replication?

Each new DNA molecule consists of one old (parent) strand and one new strand.

What is the function of helicase in DNA replication?

Helicase unzips DNA.

What does primase do in DNA replication?

Primase lays RNA primers.

What is the role of DNA polymerase?

DNA polymerase adds new nucleotides.

What does ligase do during DNA replication?

Ligase seals gaps and Okazaki fragments.

What is the function of topoisomerase?

Topoisomerase prevents supercoiling.

What was the conclusion of Griffith's experiment?

Something (DNA) transformed harmless bacteria into harmful ones.

What did Rosalind Franklin discover about DNA?

She used X-ray crystallography to show that DNA is a double helix.

What is the difference between eukaryotic and prokaryotic chromosomes?

Eukaryotes have linear, multiple chromosomes in a nucleus; prokaryotes have one circular chromosome without a nucleus.

How is DNA packaged in eukaryotes?

DNA wraps around histone proteins to form nucleosomes, which coil to form chromosomes.

What are homologous chromosomes?

Homologous chromosomes have the same genes, one from each parent.

What are sister chromatids?

Sister chromatids are identical copies of a chromosome after replication.

What are the stages of the cell cycle?

Interphase (G1, S, G2) and M phase (mitosis and cytokinesis).

How does cytokinesis differ in plants and animals?

In plants, a cell plate forms; in animals, a cleavage furrow pinches in.

What is the definition of haploid?

Haploid (n) means one set of chromosomes, as in gametes.

What is the definition of diploid?

Diploid (2n) means two sets of chromosomes, as in body cells.

What is an oncogene?

A mutated proto-oncogene that causes uncontrolled cell division, leading to cancer.

What are tumor suppressor genes?

They function as brakes of the cell cycle; mutations can lead to cancer.

What is the function of the p53 protein?

p53 checks for DNA damage and stops cell division when needed.

What is the final product of mitosis?

Mitosis produces 2 identical diploid cells.

What is the final product of meiosis?

Meiosis produces 4 genetically different haploid cells.

What is an advantage of sexual reproduction?

It provides genetic variation, which can enhance survival.

What is a zygote?

A fertilized egg formed from the union of sperm and egg.

What is nondisjunction?

Nondisjunction is the failure of chromosomes to separate, leading to disorders like Down syndrome.

What is crossing over?

Crossing over occurs in prophase I of meiosis and involves the exchange of DNA, creating genetic variation.

Who was the first person to study inheritance?

Gregor Mendel.

What is a genotype?

A genotype refers to the genetic letters (e.g., AA, Aa, aa).

What is a phenotype?

A phenotype is the physical trait expressed.

What does dominant mean in genetics?

A dominant allele is expressed with just one copy.

What does recessive mean in genetics?

A recessive allele must be homozygous to be expressed.

What is the difference between homozygous and heterozygous?

Homozygous has the same alleles (AA or aa); heterozygous has different alleles (Aa).

What is codominance?

Codominance occurs when both alleles are expressed, such as in AB blood type.

What is incomplete dominance?

Incomplete dominance results in a blend of traits, such as pink flowers.

What is polygenic inheritance?

Polygenic inheritance involves multiple genes affecting a trait, such as skin color.

What are multiple alleles?

Multiple alleles refer to a gene that has more than two forms, like blood type.

What does sex-linked mean?

Sex-linked refers to genes located on the X chromosome.

What is the purpose of PCR?

PCR (Polymerase Chain Reaction) makes millions of copies of DNA.

What is gel electrophoresis?

Gel electrophoresis separates DNA by size using electricity.

What organism is commonly used to produce insulin?

Genetically modified E. coli.

What is the central dogma of molecular biology?

The central dogma is DNA → RNA → Protein.

What are the two main steps of gene expression?

Transcription (in the nucleus) and translation (at the ribosome).

What types of RNA are there?

mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA).

What happens if DNA is mutated?

A mutation may change the protein's shape, function, or prevent it from being made.

What are the types of mutations?

Silent, nonsense, deletion, insertion, and substitution.

What does it mean if DNA has methylated histones?

It indicates that genes are turned OFF.

What occurs if mRNA is ubiquitinated?

It is marked for destruction.

How can mRNA be degraded?

By adding enzymes or removing the 5' cap and poly-A tail.

What is the function of CRISPR?

CRISPR is used for gene editing to cut or replace DNA sequences.

What is the definition of a genome?

A genome is all the DNA in an organism.

What are the shapes of bacteria?

Coccus (round), bacillus (rod), spirillum (spiral).

What are the methods of prokaryotic horizontal gene transfer?

Conjugation (pili transfer), transduction (virus transfers DNA), and transformation (picks up DNA from the environment).

What are the steps of viral infection?

Attach, inject, replicate, assemble, and release.

What is the difference between lytic and lysogenic cycles?

Lytic results in immediate destruction of the host cell; lysogenic involves viral DNA hiding in host DNA.

What is natural selection?

Natural selection is the process where organisms best suited to their environment survive and reproduce.

What is Hardy-Weinberg equilibrium?

It describes a population that is not evolving, requiring no mutation, no migration, a large population, random mating, and no natural selection.

What are the types of selection in evolution?

Directional (shift to one extreme), stabilizing (average favored), and disruptive (extremes favored, middle lost).