Chapter 6- Dr. Kim

Chromosome variation is called ____.

rearrangement

What are the stable ends of chromosomes?

telomeres

centromere

constricted region of the chromosome where the kinetochores form and spindle microtubules attache

Four major types of chromosomes

metacentric, submetacentric, acrocentric, telocentric

metacentric chromosome

Submetacentric

Acrocentric chromosome

telocentric chromosome

Karyotype

the complete set of chromosomes in an organism

How are karyotypes presented?

as a picture of metaphase chromosomes

Different staining methods present different _____.

banding patterns

Chromosome mutations

variations in the number and structure of chromosomes

What are the types of chromosome mutations?

duplication, deletion, inversion, translocation

What happens during chromosome duplication?

a segment of the chromosome is duplicated

AB*CDEFG--> AB*CDEFEFG

Tandem Duplication

AB*CDEFG-->AB*CDEFGEF

Displaced Duplication

AB*CDEFG-->AB*CDEFFEG

Reverse Duplication

What must the EF do to allow the homologous sequences of the chromosome to align?

the duplicated EF region must loop out

What does unbalanced gene dosage lead to?

developmental abnormalities

What may be affected by the relative amounts of gene products?

development

Developmental processes often require _____.

the interaction of many genes

What happens in chromosome deletion?

a segment of the chromosome is deleted

When are many deletions lethal?

in the homozygous state

Why are many genes lethal in the homozygous state?

due to the loss of essential genes

What are the effects of individuals being heterozygous for deletion?

-imbalances in the amounts of genes produced

-deleted dominant allele allows the undeleted recessive allele to express

-some genes require two copies for normal function

pseudodominance

Deleted dominant allele allows the undeleted recessive allele to express

haploinsufficient gene

some genes require two copies for normal function

When does the normal chromosome loop out during chromosome pairing?

prophase I

Cri-du-chat syndrome

"cry of the cat"

Where is the deletion of the cri-du-chat syndrome?

deletion on the short arm of chromosome 5

What happens in during the inversion of a chromosome?

a segment of the chromosome is turned 180 degrees

AB*CDEFG --> AB*CFEDG

Paracentric inversion

AB*CDEFG --> ADC*BEFG

Pericentric inversion

What are the effects on gene function?

disruption of genes

position effect

Where does the disruption of genes occur?

at the chromosomal break & insertion site

What forms in prophase I of meiosis, which allows homologous sequences to align?

an inversion loop

What does chromosome 4 differ in?

humans and chimpanzees

In a translocation, a segment of a chromosome moves from one chromosome to a ______ chromosome or to another place on the same chromosome.

nonhomolgous

Where does the position effect happen?

under the control of different regulatory sequences

Robertsonian Translocation

Long arms of two acrocentric chromosomes become joined to a common centromere through translocation, generating a long metacentric chromosome

When does deletion occur?

when chromosomes are heterozygous

Robertsonian Translocation is a type of _____ translocation.

reciprocal

Aneuploidy

A change in the number of individual chromosome

Polyploidy

A change in the number of chromosome setChapter 6-2

What are the types of Aneuplodiy?

Nullisomy

monosomy

trisomy

tetrasomy

Nullisomy

loss of one homologous chromosome pair (2n-2)

Monosomy

loss of a single chromosome (2n-1)

Trisomy

one extra chromosome (2n+1)

Tetrasomy

one extra chromosome pair (2n+2)

What are the major causes of aneuploidy?

1) deleted centromere

2)Robertsonian Translocation

3)Nondisjunction

Deleted centromere

Chromosome may be lost during mitosis or meiosis

Robertsonian translocation

Small chromosome lost during mitosis or meiosis

Nondisjunction

Failure of separation of homologous chromosomes or sister chromatids during mitosis or meiosis

Major consequences

abnormal gene dosage

abnormal gene dosage

Interferes with normal development

Uniparental disomy is a type of _____.

Aneuploidy

Uniparental Disomy

An individual has two copies of a chromosome from one parent and no copy from the other

When may uniparental disomy arise?

when trisomic embryo loses one of the triplicate chromosomes early in development

Mosaicism

Different cells within the same individual have different chromosome constitutions (Due to nondisjunction in a mitotic division)

autopolyploidy aries from:

accidents of meiosis or mitosis

Allopolyploidy arises from:

hybridization between two species

What kind of polyploids are likely to be fertile because of potential for equal segregation during meiosis?

Even-numbered polyploids

What kind of polyploids have unpaired chromosomes and usually are sterile?

Odd-numbered polyploids

Most seedless fruits are ____.

triploid

Homologous chromosomes can pair or not pair during _____.

meiosis

What level of polyploids do not usually produce viable offspring?

triploids

Allopolyploidy is the hybridization between two ____.

species

Amphidiploid

Two combined diploid genomes

In polyploidy, what is cell volume associated with?

nuclear volume which is determined by genome size

Many polyploids are physically larger than diploids

true

____ are common in crop plants.

polyploids

A diploid species has 2n = 52 chromosomes. If you found monosomy in a member of this species, how many chromosomes would it have?

51

If a diploid species (2n) has 52 chromosomes,how many chromosomes would a triploid have?

78