Lecture 2: Chromosomal Basis of Heredity

Question 1

Composition of CHROMOSOME

Answer 1

• chain of NUCLEOSOME (forms chromatin fiber)

loops into a LOOP DOMAIN

Question 2

Composition of nucleosome (2)

Answer 2

• nucleosome core (made of histones)
• DNA (twisted around nucleosome core)

Question 3

Main Parts of the CHROMOSOME

1. Chromatids (1)
2. Centromere (2)
3. Telomere (1)
4. Kinetochore (1)

Answer 3

1. One of the two identical halves of a chromosome
2. Joins sister chromatids together
   Region where spindle fibers attach during cell division (via the kinetochore)
3. Repetitive DNA sequences at the ends of chromosomes to protect against damage and uncoiling
4. Large protein assemblies that help spindle fibers attach to the centromere

Question 4

CHROMOSOMES

p-arm VS q-arm

Answer 4

p-arm - SHORT ARM

q-arm - LONG ARM

Question 5

Chromosomes carry ___?

Answer 5

genes

Question 6

What can destroy nucleosome cores in chromosomes?

and WHAT can that chemical NOT destroy?

Answer 6

dextran sulfate

can NOT destroy PROTEIN SCAFFOLD (non-histone protein)

Question 7

Nucleolus Organizer Region

definition

Answer 7

segments of chromosomes that contain the SATELLITE responsible for ribosomal RNA

Question 8

Types of Chromosomes BASED ON CENTROMERE (4)

Answer 8

1. Telocentric (walang chromatid sa taas) - TERMINAL
2. Acrocentric
3. Submetacentric
4. Metacentric (fully may chromatid) - MEDIAN

Question 9

GENOME

• denoted by ___
• definition (2)

*True Diploid is equal to??

Answer 9

X

• complete set of genes from parents
• basic chromosome number

*true diploid x = n

Question 10

GENE vs GENOME

Answer 10

A gene is a segment of DNA

While a genome is the complete set of DNA in an organism

Question 11

Somatic Chromosome Number

• definition

Answer 11

Other term for DIPLOID NUMBER (2n)

Question 12

Gametic Chromosome Number

• definition

Answer 12

Other term for HAPLOID NUMBER (n)

Question 13

Other term for the ff:

• Mitosis
• Meiosis 1
• Meiosis 2

Answer 13

• equational division
• reductional division
• equational division

Question 14

PROPHASE (3)
METAPHASE (2)
ANAPHASE (2)
TELOPHASE (3)

Answer 14

Prophase:
- chromatin condenses
- nuclear membrane disintegrates
- spindle fibers form

Metaphase:
- chromosomes line up at the EQUATORIAL PLANE
- spindle fibers attach to chromosomes

Anaphase:
- sister chromatids are separated towards opposite poles
- now, each chromatid has its own centromere

Telophase:
- chromosomes become less condense
- nuclear membrane reforms
- spindle fibers disintegrates

CYTOKINESIS

Question 15

MEIOSIS 1

Prophase (5)
Metaphase
Anaphase
Telophase

Answer 15

P:
- LEPTONEMA: chromosomes, which are thin and thread-like, begin to condense
- ZYGONEMA: homologous pairs undergo SYNAPSIS to form a BIVALENT (4 chromatids)
- PACHYNEMA: homologous pair intertwine and crosses over @ CHIASMA
- DIPLONEMA: homologous pair separate from intertwining BUT remain attached at chiasma
- DIAKINESIS: homologous pairs are MAXIMALLY condensed
: spindle fibers formed
: nucleus and nuclear membrane disintegrates

M: homologous pairs align at the middle

A: homologous pairs separate towards opposite poles, forming UNIVALENTS (2 chromatids)

T: chromosomes become less condense
: nuclear membrane reforms
: spindle fibers disintegrates

CYTOKINESIS

Question 16

MEIOSIS 1

Ploidy Level of daughter cells at end of MEIOSIS 1

Answer 16

2 genetically different haploid daughter cells

Question 17

Effect of Diplonema

Answer 17

Genetic Recombination

Question 18

Frequency of CROSSING OVER of HOMOLOGOUS PAIRS

Answer 18

At least ONCE per pairf