Genetics Chapter 8

metacentric

metacentric

a chromosome in which the centromere is near the middle

submetacentric

a chromosome in which the centromere is slightly off center

acrocentric

a chromosome in which the centromere is significantly off center, but not at the end

telocentric

a chromosome in which the centromere is at one end

karyotype

a photographic representation of all the chromosomes within a cell; reveals how many chromosomes are within an actively dividing somatic cell

G banding

the process of staining chromosomes with a Giemsa stain to produce a unique banding pattern

deletion

a condition in which a segment of DNA is missing

duplication

the repetition of a segment of DNA within a single chromosome or genome

inversion

a change in the orientation of genetic material along a chromosome such that a segement is flipped or reversed from the normal order

translocation

a rearrangement in which one segment of a chromosome breaks off and becomes attached to a different chromosome or a different part of the same chromosome

simple translocation

a rearrangement in which a piece of a single chromosome becomes attached to a different chromosome

reciprocal translocation

a rearrangement in which two different chromosomes exchange pieces, altering both of them

terminal deletion

a deletion in which a segment is lost from the end of a linear chromosome

interstitial deletion

a deletion in which an internal segment is lost from a chromosome

repetitive sequences

short DNA sequences that appear many times within a species’ genome

pericentric inversion

an inversion in which the centromere is located within the inverted region of the chromosome

paracentric inversion

an inversion in which the centromere is found outside the inverted region

inversion heterozygote

a diploid individual that carries one normal chromosome and a homologous chromosome with an inversion

inversion loop

the loop that is formed when the homologous chromosomes of an inversion heterozygote attempt to align (synapse) during meiosis

acentric fragment

a fragment of a chromosome that lacks a centromere

dicentric

a chromosome with 2 centromeres

dicentric bridge

the region between the two centromeres in a dicentric chromosome

telomeres

specialized repeated sequences found at the ends of eukaryotic chromosomes

balanced translocations

a translocation, such as a reciprocal translocation, in which the total amount of genetic material remains normal or nearly normal

unbalanced translocations

a translocation in which a cell has too much or too little genetic material compared to a normal cell

Robertsonoian translocation

the structure produced when 2 nonhomologous acrocentric chromosomes fuse at their short arms

euploid

an organism in which the chromosome number is an exact multiple of a chromosome set

triploid

an organism or cell with 3 sets of chromosomes

tetraploid

an organism or cell with 4 sets of chromosomes

polyploid

an organism or cell with more than 3 sets of chromosomes

aneuploid

a variation in chromosome number in which the total number of chromosomes is not an exact multiple of a set

trisomic

a diploid cell or organism with one extra chromosome (2n+1)

monosomic

a diploid cell or organism with one fewer chromosome (2n-1)

nondisjunction

an event in which chromosomes don’t segregate properly during mitosis or meiosis

mosaicism

a condition in which an indivudal has 2 or more genetically different sets of cells in their body

Trisomy 13

Patau Syndrome; results in mental and physical deficiences, organ defects, large triangular nose, eand early death

Trisomy 18

Edward Syndrome; results in mental and physical deficiences, facial abnormalities, extreme muscle tone, and early death

Trisomy 21

Down Syndrome; results in mental deficiences, abnormal pattern of palm creases, slanted eyes, flattened face, and short stature

XXY

Klinefelter Syndrome; results in sexual immaturity and breast swelling (male)

XYY

Jacobs Syndrome; results in tall and thin stature (male)

XXX

Triple X Syndrome; tall and thin stature and menstrual irregularities (female)

X0

Turner Syndrome; results in short stature, webbed neck, and sexually undevelopped individuals (female)