Genetics Unit 2 Vocab

Linkage

Genes located close together on the same chromosome that tend to be inherited together.

Recombination frequency

The percentage of recombinant offspring used to estimate distances between genes.

Genetic mapping

The process of determining the location and relative distances between genes.

Map units (centimorgans, cM)

A unit of measurement for genetic linkage, where 1 cM = 1% recombination.

Three-point testcross

A genetic cross used to determine the relative order of three genes.

Interference

The phenomenon where one crossover event reduces the probability of another nearby.

Coefficient of coincidence

A ratio measuring the observed double crossover frequency compared to the expected.

Parental (non-recombinant) gametes

Gametes that retain the original allele combinations from the parents.

Recombinant gametes

Gametes with new allele combinations due to crossing over.

Complete linkage

The situation where no recombination occurs between genes.

Incomplete linkage

The occurrence of some recombination between linked genes.

Syntenic genes

Genes located on the same chromosome.

Physical map

A chromosome map based on actual DNA sequence distances (measured in base pairs).

Conjugation

The process of direct transfer of DNA between bacterial cells via a pilus.

Transformation

The uptake and incorporation of foreign DNA from the environment into a bacterial genome.

Transduction

The process by which bacterial DNA is transferred via a bacteriophage.

Plasmid

A small, circular DNA molecule that replicates independently of the bacterial chromosome.

F factor (fertility factor)

A plasmid that enables bacterial conjugation.

Hfr strain (high-frequency recombination strain)

A bacterium with the F factor integrated into its chromosome.

F’ (F-prime) plasmid

A plasmid that carries bacterial chromosomal genes.

Lytic cycle

A viral reproductive cycle where new phages are produced, leading to cell lysis.

Lysogenic cycle

A viral cycle where the phage DNA integrates into the host genome and replicates passively.

Prophage

Viral DNA that is integrated into the bacterial chromosome.

Generalized transduction

The transfer of random bacterial genes by a phage.

Specialized transduction

The transfer of specific bacterial genes by a lysogenic phage.

Competence

The ability of a bacterial cell to take up foreign DNA during transformation.

Transposons

Mobile genetic elements that can move between different locations in the genome.

Nucleotide

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

Purines

Double-ring nitrogenous bases (adenine, guanine).

Pyrimidines

Single-ring nitrogenous bases (cytosine, thymine, uracil).

Complementary base pairing

A-T (DNA), A-U (RNA), and G-C via hydrogen bonds.

Chargaff’s rules

The observation that DNA has equal amounts of A and T, and G and C.

X-ray diffraction

A technique used by Rosalind Franklin to reveal DNA’s helical structure.

Antiparallel strands

The orientation of DNA strands, where one runs 5' to 3' and the other 3' to 5'.

Denaturation (DNA melting)

The separation of DNA strands due to heat or chemical treatment.

Renaturation (reannealing)

The reformation of double-stranded DNA from single strands.

Hyperchromic shift

The increase in UV light absorption as DNA denatures.

Supercoiling

The overwinding or underwinding of DNA to fit into the cell.

Nucleoid

The region where bacterial DNA is found in prokaryotes.

Histones

Proteins that help organize and package eukaryotic DNA into chromatin.

Semiconservative replication

Each new DNA molecule consists of one old and one new strand.

Replication fork

The Y-shaped region where DNA is unwound and copied.

Helicase

The enzyme that unwinds DNA strands.

Single-stranded binding proteins (SSBs)

Proteins that prevent reannealing of single-stranded DNA.

Primase

The enzyme that synthesizes RNA primers for DNA polymerase to begin replication.

DNA polymerase III

The main enzyme responsible for DNA synthesis in bacteria.

Leading strand

The continuously synthesized DNA strand in the 5’ to 3’ direction.

Lagging strand

The discontinuously synthesized strand that forms Okazaki fragments.

Okazaki fragments

Short DNA segments synthesized on the lagging strand.

DNA ligase

The enzyme that seals gaps between Okazaki fragments.

Topoisomerase (gyrase)

The enzyme that relieves supercoiling tension in DNA.

Telomeres

The repetitive DNA sequences at the ends of eukaryotic chromosomes.

Telomerase

The enzyme that extends telomeres, preventing chromosome shortening.

Chromatin

The complex of DNA and proteins in the nucleus of eukaryotic cells.

Nucleosome

The fundamental unit of chromatin, consisting of DNA wrapped around histone proteins.

Euchromatin

Loosely packed chromatin associated with active gene expression.

Heterochromatin

Tightly packed chromatin associated with gene repression.

Histone modification

Chemical changes to histone proteins that affect gene regulation.

DNA methylation

The addition of methyl groups to DNA, often silencing genes.

Epigenetics

The study of heritable changes in gene expression that do not involve changes in DNA sequence.

Tandem repeats

Repetitive DNA sequences that occur in a head-to-tail arrangement.

Satellite DNA

Highly repetitive DNA sequences found in centromeres and telomeres.

Transposable elements (jumping genes)

DNA sequences that can move within the genome.

Pseudogenes

Nonfunctional sequences of DNA that resemble functional genes.

Centromere

The region of a chromosome that connects sister chromatids and attaches to spindle fibers.

Kinetochore

The protein complex that forms at the centromere and interacts with spindle fibers.