Biology: DNA, Cell Cycle, and Genetics

These flashcards summarize key concepts in DNA structure, cell cycle processes, and genetic principles.

Sugar-phosphate backbone

Forms the outer framework of DNA and provides stability through strong covalent bonds.

Antiparallel strands

The two DNA strands run in opposite directions (5'→3' and 3'→5') for proper replication.

Helicase

An enzyme that unwinds the DNA by breaking hydrogen bonds between base pairs.

Semiconservative replication

Each new DNA molecule contains one original strand and one newly synthesized strand.

Uracil

A nitrogenous base found in RNA that replaces thymine in DNA, indicating a different structure and function.

Nucleotide

The building block of DNA and RNA, consisting of a sugar, phosphate group, and nitrogenous base.

Hydrogen bonds

Weak bonds that allow DNA strands to separate easily during replication while maintaining stability.

Frameshift mutation

A genetic mutation caused by the deletion or insertion of nucleotides, altering downstream protein sequences.

Interphase

The phase of the cell cycle where cells grow, perform functions, and prepare for division.

S phase

The phase of the cell cycle in which DNA is replicated to form sister chromatids.

Metaphase

The stage of cell division where chromosomes align in the center of the cell for proper separation.

Mitosis

The process of cell division that allows for growth, repair, and cell replacement.

Anaphase

The stage of mitosis where sister chromatids separate and move to opposite poles of the cell.

Spindle fibers

Structures that attach to chromosomes and pull them apart during cell division.

Cytokinesis

The division of the cytoplasm to form two separate cells after mitosis.

Cancer

A disease characterized by uncontrolled cell division due to loss of regulation in the cell cycle.

Prophase

The first stage of mitosis where chromosomes condense, spindle forms, and the nuclear membrane breaks down.

Phenotype

The observable traits of an organism resulting from the interaction of its genotype with the environment.

Genotype

The genetic makeup of an organism influencing its traits and characteristics.

Heterozygous

An organism possessing two different alleles for a specific trait.

Law of Segregation

The principle that alleles separate during gamete formation, leading to individual inheritance of traits.

Blood type inheritance

From a Type O × Type AB cross, offspring can exhibit either Type A or Type B blood types.

Sex-linked trait

A trait determined by a gene located on a sex chromosome, often associated with X-linked inheritance.

Incomplete dominance

A genetic situation in which a blended phenotype appears in the offspring (e.g., red + white = pink).

Polygenic trait

A trait controlled by multiple genes, resulting in continuous variation among individuals.

Probability of bb from Bb × Bb

There is a 25% chance (1 out of 4) of obtaining the homozygous recessive genotype bb.

Pedigree

A diagram that shows inheritance patterns of traits across generations in a family.

Purpose of meiosis

To produce haploid gametes for sexual reproduction, ensuring genetic diversity.

Crossing over

The exchange of genetic material between homologous chromosomes during meiosis, increasing genetic variation.

Central Dogma

The flow of genetic information from DNA to RNA to protein.

Translation

The process where ribosomes synthesize proteins based on the sequence of codons in mRNA.

Codon

A three-base sequence in mRNA that codes for a specific amino acid during protein synthesis.

Transcription

The process whereby the DNA sequence is copied into mRNA by RNA polymerase.

Silent mutation

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

Dominant allele

An allele that is expressed phenotypically even when only one copy is present.

Recessive allele expression

A recessive allele is only expressed when two copies are present (homozygous recessive).