EXAM 3 - Mutations: source of genetic change

metacentric

centromere in the middle, making the two arms roughly equal

submetacentric

centromere slightly off center, making one arm short

acrocentric

centromere close to one end, making one arm very short

telocentric

centromere at the end of the chromosome

centromere location

helps determine the chromosome’s shape and classification

euploidy

normal chromosome sets

polyploidy

more than two complete chromosome sets

triploid

having three complete sets

tetraploid

having four complete sets

aneuploidy

having an extra or missing individual chromosome

trisomy

having one extra copy of a particular chromosome, 2n+1

monosomy

one copy of a particular chromosome is missing, 2n-1

gene dosage

amount of a gene present, which can affect how much of its product is made

down syndrome

• trisomy 21

• 47 + 21

turner syndrome

• 45, X

• has one X chromosome and lacks a second sex chromosome

klinefelter syndrome

• 47, XXY

• has an extra X chromosome

patau syndrome

• trisomy 13

• 47, + 13

edwards syndrome

• trisomy 18

• 47, + 18

embryonic lethal

a genetic change that prevents an embryo from surviving

nondisjunction

when chromosomes fail to separate correctly during cell division

what should happen in meiosis I?

homologous chromosomes should separate

what should happen in meiosis II

sister chromatids should separate

nondisjunction in meiosis I

• two gametes n + 1

• two gametes n - 1

nondisjunction in meiosis II

• two normal gametes

• one gamete n + 1

• one gamete n - 1

breakage and rejoining

a chromosome breaks, and the pieces rejoin incorrectly

recombination between repetitive DNA

similar DNA sequences can recombine in the wrong places, causing rearrangements

deletion

a segment is lost

duplication

a segment is copied

inversion

a segment flips around

translocaiton

a segment moves to a different chromosome location

insertion

DNA is inserted into a chromosome

transposable element

a DNA sequence that can move to a different location in the genome

recombination

exchange of DNA between chromosomes

balanced rearrangement

chromosome material is rearranged without an overall gain or loss of DNA

• inversions

• reciprocal translocations

unbalanced rearrangement

chromosome material is gained or lost, changing gene dosage

• deletions

• duplications

• insertions of additional DNA

pericentric inversion

includes the centromere

results of crossover in pericentric inversions

chromosomes with duplications and deletions

paracentric inversion

doesn’t include the centromere

results of crossover in paracentric inversions

dicentric bridge and an acentric fragment

• dicentric bridge can break during anaphase I

inversion heterozygote

one chromsome is inverted but the other homologue is not

crossover

exchange of DNA between homologous chromosomes during meiosis

dicentric chromosome/ chromatid

two centromeres

acentric fragment

chromosome fragment with no centromere

reciprocal translocaiton

two nonhomologous chromosomes break and exchange segments

nonhomologous chromosomes

chromosomes that are not a matching homologous pair

bone marrow

tissue that produces blood cells (red blood cells, white blood cells, platelets)

leukocytes

white blood cells

leukemia

cancer involving blood-forming tissues that causes abnormal blood cell production

chronic myelogenous leukemia (CML)

• associated with the reciprocal translocation that creates the philadelphia chromosome

• joins parts of the BCR and ABL genes to create the BCR-ABL fusion gene

fusion gene

a gene formed by joining parts of two different genes

protein kinase

an enzyme that adds phosphate groups to proteins and affects cell signaling

constitutively active

continuously active rather than switching on only when needed

PCR (polymerase chain reaction)

can be used to detect the translocation

primer

a short piece of DNA that identifies where PCR copying begins

PCR product

DNA segment produced during PCR

tandem duplication

duplicated segment is directly next to the original segment

dispersed (nontandem) duplication

duplicated segment is located somewhere else on the same chromosome or on a different chromosome

same orientation

duplicated segment points in the same direction as the original

reverse orientation

duplicated segment points in the opposite direction

transposable element

DNA sequence that can move from one location to another within the genome

regulatory region

DNA region that helps control when, where, or how much a gene is expressed