UNIT 2 BIOLOGY SBI3U

Question 1

INTERPHASE? WHAT HAPPENS

Answer 1

Interphase 3 phases, G1, S, G2
Is the stage where a. cell carries out its normal function, grows, and makes copies of its genetic material.
G1- synthesizing new molecules (the longest phase of interphase)
SYNTHESIS - cellularDNA IS COPIED OR REPLICATED
G2 - Cell synthesizes more molecules

Question 2

WHAT HAPPENS DURING MITOSIS?

Answer 2

during mitosis, the cells copied genetic material separates and the cell prepares to split into two daughter cells. PROPHASE, METAPHASE, ANAPHASE, TELAPHASE

Question 3

PROPHASE?

Answer 3

• cell chromatin condensed into CHROMOSOMES
  Each chromosome in prophase exits as two copies of one chromosome

Question 4

METAPHASE

Answer 4

The spindle fibres guide the chromosomes to the equator of the cell
Meta = middle
Each pair of sister chromosomes are considered a single chromosome as long as they are conjoined by the centromere

Question 5

ANAPHASE?

Answer 5

• each sister chromotid and centromere seperate and split to opposite poles of cell
• seperate sister chromatids are now chromosomes
• spindle fibres shorten

Question 6

TELAPHASE?

Answer 6

Telephase begins when chromosomes have reached opposite poles of cell
Chromosomes start to unwind into less visible strands of chromotid

Question 7

What are homologous chromosomes

Answer 7

Paired chromosomes that appear similar in terms of their length, centromere location

Question 8

CYTOKENISIS?

Answer 8

during cytokinesis, the sides of a cell pinch inward, dividing the cytoplasm and forming two daughter cells, each containing a complete copy of the parents cells DNA.

Question 9

ANIMAL CELLS?

Answer 9

• an indentation forms in the cell membrane along the equator of the cell
• this indentation deepens unit the cell is pinched into twi
• the cytoplasm divides equally between the two halves of the cell

Question 10

PLANT CELLS?

Answer 10

• has a rigid cell wall covering its cell membrane
  -this cell wall is much stronger than animals
• cell wall does NOT pinch inward
• A cell plate forms between the two daughter nuclei and cell wall forms on other side of cell plate

Question 11

WHAT IS MEIOSIS??

Answer 11

The cellular process that produces cells containing half the number of chromosomes as the parent cell
CROSSING OVER OCCURS IN PROPHASE I

Question 12

WHY IS MEIOSIS IMPORTANT??

Answer 12

the purpose of meiosis is to produce gametes and allow the cell to have genetic diversity in males. meiosis happens in the test and in females. meiosis happens in the ovarie. meoisis undergoes 2 sets of division to produce 4 haploud daughter cells that are not identical .

Question 13

spermatogenesis vs oogenisis

Answer 13

spermatogenesis - the process of sperm production
\ in most animals, meiosis takes place in testicales and the process starts with a diploid cell.
in meiosis ii the cell undergoes a final set of development to turn into a mature sperm.
oogenisis- the process of egg production

Question 14

HOMOLOGOUS CHROMSONES VS SISTER CHROMATIDS

Answer 14

• homologous chromosomes may NOT carry identical information while sister chromatids do.
• homologous chromosomes do not stick together while sister chromatids are joined together by their centromere
• homologous chromosomes are the two chromosomes that makes a chromosone pair and sister chromatids are the duplicate of each of the pair of homologous chromosomes.

Question 15

WHY IS CROSSING OVER IMPORTANT??

Answer 15

crossing over is important because it helps create our genetic diversity and our individuality. during prophase 1. snapesis is the aligning of homologous chromosones

Question 16

INDEPENDENT ASSORTMENT??

Answer 16

during metaphase I, chromosomes are arranged in homologous pairs along the equator of the cell and in each pair the chromosome of the maternal origin is orientated toward one pale of the cell and the chromosome of paternal origin is oriented toward the other pole
this orientation of each pair of chromosomes is the independent of the orientation of the other pairs.

Question 17

Downs

Answer 17

trisonomy 21

Question 18

EDWARDS

Answer 18

TRISONOMY 18

Question 19

PATAU

Answer 19

TRISONOMY 13

Question 20

KLINEFELTER

Answer 20

XXYY

Question 21

TURNERS

Answer 21

XO

Question 22

non disjunction

Answer 22

During meiosis when homologous chromosome pairs or sister chromatids do not separate as they should -called non-disjunction’s

Question 23

monosomy meaning

Answer 23

The absence of one pair of chromosomes

Question 24

WHY IS MEIOSIS SO SIGNIFICANT??

Answer 24

meiosis is significant because it allows sexual reproduction of diploid organisms.
it enables genetic diversity, and it aids the repair of genetic defects

Question 25

ERRORS IN MEIOSIS?

Answer 25

there can be errors in number or structure of chromosome.
during crossing over, the chemical bonds that hold DNA together in the chromosome are broken and reformed, sometimes the chromosome does not reform correctly or non-homologous chromosome pairs may cross over.
other times homologous chromosome pairs or sister chromatids do not seperate as they should during meiosis.

Question 26

COMPLETE DOMINANCE?

Answer 26

When the dominant allele completely masks the effect of the recessive allele

Question 27

INCOMPLETE DOMINANCE?

Answer 27

a condition in which neither allele for a gene completely conceals the presence of the other. it results in INTERMEDIATE EXPRESSION of a trait

Question 28

CODOMINANCE?

Answer 28

the condition in which both alleles for a. trait are equally expressed in a heterozygote; both alleles are dominant in codominance.
SICKLE CELL ANEMIA IS AN EXAMPLE OF CODOMINANCE

Question 29

MULTIPLE ALLELES?

Answer 29

TYPES:
type A
= I^A I^A - HOMOZYGOTE
= I^A i - HETEROZYGOTE

type B
= I^B I^B - HOMOZYGOTE
= I^B i - HETEROZYGOTE

type AB
= I^A I^B - HETEROZYGOTE

Type O
= ii - HOMOZYGOTE

Question 30

SEX-LINKED TRAITS?

Answer 30

• many sex-linked traits in humans are genetic disorders
• if a disorder is x-linked DOMINANT affected MALES pass the alleles only to daughters who have 100% chance of having the disorder.
• females can pass on x-linked dominant alleles to both sons and daughters
• most sex linked inherited traits in humans are x-linked recessive traits, therefore, males only need to inherit one allele to be affected but females need both alleles to be affected
• thus, x-linked recessive traits affect more males than females in a family.

Question 31

DIFFFERENCE BETWEEN MITOSIS AND MEIOSIS

Answer 31

mitosis
- 4 stages
-happens in somatic cells
- purpose is cellular proliferation
- produces 2 diploid daughter cells
- chromosome number remains the same
- genetic variation doesnt change

meoisis
- 8 stages
- happens in body cells
- purpose is sexual reproduction
- produces 4 haploid daughter cells
- chromosome number is halved in each cell
- genetic variation increased