Lecture 15

Question 1

Modifications at level of chromosome

Answer 1

phenotypic variation result from changes of individual genes

Question 2

Chromosome mutations and aberrations

Answer 2

• total number of chromosomes vary
• deletion
• duplication
• rearrangements

Question 3

Duplication

Answer 3

BC –> BCBC

Question 4

Deletion

Answer 4

ABCD –> ACD

Question 5

Inversion

Answer 5

BCD –> DCB

Question 6

Nonreciprocal translocation

Answer 6

part of a chromosome attaches to a different one

Question 7

Reciprocal translocation

Answer 7

2 chromosomes swapping parts of there body

Question 8

Deletions and duplications

Answer 8

total amount of genetic information in chromosome changes

Question 9

Inversions and translocations

Answer 9

genetic remains the same but rearranged

Question 10

Deletions

Answer 10

• missing regions of chromosomes
• chromosome breaks in one or more places
• portion is lost

Question 11

Location of deletion can vary…

Answer 11

• terminal deletion - near one end
• intercalary deletion - interior of the chromosome

Question 12

Compensation loop

Answer 12

• synapsis between chromosome with large intercalary deletion and normal complete homolog
• requires unpaired region of normal homolog to loop out of linear structure into deletion or compensation loop
• the looped area is still conserved on the strand it is just not in the linear structure

Question 13

Cri du chat syndrome

Answer 13

• deletion of small terminal part of chromosome 5 (on p region)
• segmental deletion
• infants exhibit anatomical malformations

Question 14

Duplications

Answer 14

• repeated segment of chromosome
• single locus is present more than once in genome
• can produce compensation loop
• arise from unequal crossing over between synapsed chromosomes during meiosis

Question 15

Gene redundancy

Answer 15

• example RNA:
  
  • multiple copies of genes encode for ribosomal RNA genes
  • this DNA is called rDNA

Question 16

Gene amplification

Answer 16

• mechanism that increases rRNA
• oocyte store nutrients including ribosomes (preloaded)
• used by embryo in early development for rRNA synthesis

Question 17

Barr Bodies

Answer 17

• condensed X chromosome that doesn’t need to be displayed for an organisms with XX or more
• N-1 when N= the amount of X chromosomes

Question 18

Bar mutation - drosophila

Answer 18

• duplications cause phenotypic variation
• bar-eye phenotype in drosophila results from duplication
• bar-eyed flies have narrow, slit-like eyes
• inherited phenotype
• mutation is inherited

Question 19

Gene duplication may play a role in evolution…

Answer 19

gene duplication hypothesized to be major source of new genes
- hypothesis supposed by discovery of genes with substantial amount of DNA sequence in common, but distinct gene products

Question 20

CNVz: Copy number variants

Answer 20

• represent quantitative differences in number of large DNA sequences
• found in coding and noncoding regions of genome
• play crucial role in the expression of traits (either up or down regulate)

Question 21

Inversion

Answer 21

• rearrangement of linear gene sequence
• no loss of genetic information
• segment of chromosome turned 180 degrees (flipped)
• requires 2 breaks in chromosome, and reinsertion inverted segment
• may arise from chromosomal looping

Question 22

paracentric inversion

Answer 22

• does not change lengths of two arms of chromosome
• centromere not part of inverted segment

Question 23

pericentric inversion

Answer 23

• centromere is part of inverted segment
• does change length of two arms of chromosomes

Question 24

inversion loops

Answer 24

• inverted and non-inverted chromosomes in meiosis paired only if they form an inversion loop

Question 25

Paracentric inversion crossover

Answer 25

- centromere not part of inverted segment - one recombinant chromatid is dicentric (two centromeres) - one is acentric (lacking a centromerre, none invovled)

Question 26

acentric inversion

Answer 26

- this new chromosome would not spilt during mitosis or meiosis because no centromere to hold onto

Question 27

pericentric inversion crossover

Answer 27

centromere is part of inverted segment - crossover between pericentric inversion and non-inverted homolog - recombinant chromatids have duplications and deletions

Question 28

translocation

Answer 28

movement of chromosomal segment to new location in genome - LINES and SINES

Question 29

reciprocal translocation

Answer 29

- involves exchange of segments between 2 non-homologous chromosomes - genetic information is either lost or gained - has unusual synapsis configuration during meiosis

Question 30

alternate segregation pattern

Answer 30

- segregation pattern that occurs at first meiotic division - has complete complement of genetic information - not losing any information

Question 31

adjacent segregation pattern

Answer 31

- leads to gametes containing duplications and deficiencies - if these participate in fertilization in animals, the resultant offspring do not usually survive - parent is said to have semi-sterility

Question 32

fragile sites

Answer 32

- more susceptible to chromosome breakage when cultured in the absence of folic acid or chemicals - sites indicate regions of non-tightly coiled chromatin - most common in X chromosomes

Question 33

Trinucleotide repeats

Answer 33

- a sequence of three nucleotides is repeated many times - expands the size of the gene

Question 34

genetic anticipation

Answer 34

- the number of trinucleotide repeats increases with every generation - carrier status: 55-230 trinucleotide repeats - syndrome status: >230 trinulceotide repeats

Question 35

Fragile sites and cancer

Answer 35

- link between autosomal fragile site and lung caner reported

Question 36

Robertsonian translocation

Answer 36

allows for down syndrome of down syndrome from chromosome 21 to 14