SBI unit 2 exam notes

Question 1

What are the stages of mitosis?

Answer 1

1. Interphase: new cell organelles form(G1, Synthesis, G2)
2. prophase: membrane and nucleus disappear, spindle fibres start forming
3. metaphase: spindle fibres attach to centromeres, chromosomes line up
4. Anaphase: centromere torn apart, chromatids pulled to opposite poles

5.Telophase: chromosomes unwind, spindle fibres breakdown and new nuclear membrane forms around new

Question 2

What are the stages of meiosis?

Answer 2

1.Interphase: growth and synthesis of chromosome

2. Prophase: pairs of homologous chromosomes line up side by side(Synapsis), chromosomes exchange legs (cross over), each chromosome now holds each parent DNA, 4 chromatids=tetrad
3. metaphase: spindle fibres fully form, tetrads **lined up in the center **of cell, chromosomes are lined up randomly (Independent assortment) so that the daughter cells have chromosomes from both parents
4. anaphase: tetrads are separated by spindles + move to opposite sides of the cell
5. telophase: homologous chromosomes uncoil and cytoplasm splits

6.** Cycle repeats** in meiosis 2 but results in** 4 gametes (haploid daughter cells** cuz chromatids not chromosomes are in the nuclia)

Question 3

What are diploids, haploids, gametes, and zygotes?

Answer 3

Diploids:cells with **2 complete sets **of chromosomes

Haploids: cells with 1 set of chromosomes

Gametes**:sex cells **ALWAYS haploids

Zygote:The fusion of 2 haploid cells

Question 4

What is
Non-disjuncsion:
Deletion:
Duplication:
Inversion:
Transolcation:

Answer 4

Non-disjuncsion: failure of the homologous chromosomes to separate during anaphase 1 of mitosis, one daughter cell has too much causng trisomy and monosomy

Deletion: chromosome is broken off

Duplication: gene sequance is reapeated

Inversion: gene sequaence breaks free and rearanges in **reverse order **

Transolcation: some parts of chromosomes swap places

Question 5

What are
Autosomal inharitance

Autosomal dominant inheritance

Autosomal receisice inheritance

Sex-linked traits

Incomplete domiance

co-dominace

Answer 5

Autosomal inharitance:phenotypes passed through autosme(body) cells

Autosomal dominant inheritance: **dominant allels **dominate

Autosomal receisice inheritance: recessive alleles are ressesive and need no dominant alleles to form phenotype

Sex-linked traits:traits attached and passed to the **x chromosomes **

Incomplete domiance: 2 dominant alles are blended (Red +White=Pink)

Co-Dominance: both dominant allies show (white +Black= spotted black and white)

Question 6

What is DNA made of?

Answer 6

Deoxyribose sugar, phosphate, and nitrogenous base/Nucleotides ( Adenine, thymine, guanine, cytosine)

Question 7

What is the central dogma of life?

Answer 7

DNA replication itself,RNA transcription/decodes the DNA, and translation the recipe to make protein. DNA →RNA → protein