Mizzou Genetics (Birchler) Exam 4 Terms

Nucleosomes

DNA wrapped around proteins to help keep it organized and packed inside the nucleus.

Histones

subunit of a nucleosome

Scaffold

A protein framework that helps hold chromosomes in their organized shape.

Scaffold Attachment Regions (SARs)

Sections of DNA that attach to the protein scaffold and help organize the chromosome.

Heterochromatin

Tightly packed DNA that is usually turned OFF or not actively being used.

Euchromatin

regions of a chromosome that stain lightly and that have most of the genes

Telomere

The structures at the very ends of chromosomes that resolve replication

Variable Number Tandem Repeats (VNTRs)

Short DNA sequences repeated over and over, with the number of repeats differing between people.

SINEs

Short pieces of DNA that can copy themselves and move to different locations in the genome.

LINEs

Longer pieces of DNA that can copy themselves and move to different locations in the genome.

Telocentric

A chromosome with the centromere at the very end.

Acrocentric

A chromosome with the centromere very close to one end.

metacentric

A chromosome with the centromere in the middle, making both arms about equal length.

Acentric

A chromosome that has NO centromere.

Holocentric

A chromosome that has spindle attachment areas spread along almost its entire length instead of having just one centromere.

Duplication

A section of a chromosome is copied, so there is an extra copy.

Inversion

A chromosome section breaks off, flips around, and attaches back in the opposite direction.

Translocation

A piece of one chromosome breaks off and attaches to a different chromosome

Asymmetric Pairing

Homologous chromosomes do not line up evenly during meiosis because their DNA arrangements are different.

Inversion Loop

This is what forms when chromosomes bend so that matching DNA sections can line up during meiosis despite an inversion.

Paracentric Inversion

An inversion that does NOT include the centromere.

Pericentric Inversion

An inversion that DOES include the centromere.

Dicentric Bridge

A chromosome with TWO centromeres that can get pulled toward opposite sides during cell division, forming a bridge.

Acentric Fragment

A chromosome piece with NO centromere, meaning it usually cannot attach to spindle fibers and may be lost during cell division.

Alternate Segregation

Type of segregation in a translocation heterozygote that produces meiotic products with all genes represented (assuming no recombination between the centromere and translocation breakpoint);

Adjacent 1 Segregation

most common type of segregation in a translocation heterozygote that produces meiotic products with deficient and duplicate chromosomal segments (assuming no recombination between the centromere and the translocation breakpoint):

Adjacent 2 Segregation

Chromosomes with HOMOLOGOUS centromeres move together, producing unbalanced gametes. This is less common

Euploid

Having a complete set of chromosomes or an exact multiple of the normal chromosome set.

Aneuploid

Having an extra or missing individual chromosome instead of a complete extra set.

Monosomic

Missing ONE chromosome from the normal diploid set (2n − 1)

Trisomic

Type of aneuploidy when three copies of a chromosome are present

Double Trisomic

Having TWO different extra chromosomes (2n + 1 + 1)

Nondisjunction

The failure of homologous chromosomes to separate properly in meiosis thus leads to aneuploid in gametes

Down Syndrome

Trisomy 21

Monoploid

Having ONE basic set of chromosomes (x)

Polyploid

Having more than two complete sets of chromosomes

Colchicine

A chemical that stops spindle fibers from working, which can prevent chromosomes from separating and cause chromosome sets to double

Autopolyploid

type of polyploid in which all chromosomes are derived from the same species

Allopolypoid

Having chromosome sets from TWO or more different species

homologous

In polyploids, nonhomologous chromosomes are nevertheless very similar in gene content

Triploidy

Having THREE complete sets of chromosomes (3n)

Quadrivalent

Four chromosomes paired together during meiosis

Trivalent

Three chromosomes paired together during meiosis

Univalent

a chromosome without a pairing partner in meiosis 1

Bivalent

Two homologous chromosomes paired together during meiosis

Nullisomic

the condition in hexaploids in which a homologous chromosome pair is missing

x

The basic number of chromosomes in one complete set of a species

n

the gametic chromosome number is designated by:

Extranuclear Genes

Genes found outside the nucleus, usually in mitochondria or chloroplasts

Cytoplasmic Genes

Genes located in the cytoplasm instead of inside the nucleus

Mitochondria

Structures inside cells that produce energy and contain their own DNA

Plastids

Structures in plant cells, including chloroplasts, that have their own DNA and help with things like photosynthesis

Cytoplasmic Segregation

The random distribution of mitochondria or other organelles into daughter cells during cell division

Maternal Effect

When an offspring's traits are determined by substances (usually proteins or RNA) placed in the egg by the mother

DNA Ligase

An enzyme that seals together different fragments of DNA during cloning

Plasmid

A small circular piece of DNA found in bacteria that is separate from the main chromosome

Isoschizomers

different restriction enzymes that cleave the same dna sequence

3' Overhang

A sticky end of DNA where the 3' strand sticks out farther than the other strand

5' Overhang

A sticky end of DNA where the 5' strand sticks out farther than the other strand

Electrophoresis

method of separation of DNA fragments in a gel in an electric field

Ethidium Bromide

A chemical dye that binds to DNA and makes it glow under UV light so DNA bands can be seen

Restriction Fragment

A piece of DNA created when a restriction enzyme cuts DNA

Restriction Map

A diagram showing where restriction enzymes cut a DNA molecule

Dideoxynucleotide

type of nucleotide used during DNA sequencing to terminate synthesis

Restriction Fragment Length Polymorphism (RFLP)

Differences in DNA fragment sizes between individuals caused by differences in DNA sequences or restriction enzyme cutting sites

Southern Blot

A technique used to find a specific DNA sequence by transferring DNA fragments onto a membrane and using a matching DNA probe

Polymerase Chain Reaction (PCR)

method used to amplify many copies of a specific sequence of DNA using primers oriented in opposite directions toward each other on sequence

CENH3

A special histone-like protein found at centromeres that helps identify where the centromere is and allows chromosomes to separate properly

mitochondria

cellular organelles involved with ATP synthesis and inherited maternally

centromere

the part of the chromosome that is involved with chromosome movement functions