Mitosis, Meiosis, Mistakes & DNA structure (QUIZ)

Question 1

What is GENETICS?

Answer 1

The branch of biology dealing with heredity and the variations of INHERITED CHARACTERISTICS

Question 2

What is HEREDITY?

Answer 2

The PASSING OF TRAITS from parents to offspring

Question 3

What are TRAITS?

Answer 3

CHARACTERISTICS or FEATURES of an organism

–> Nose, Shape, height

Question 4

Heredity: Explain DOMINATE gene (provide example)

Answer 4

Variant of a gene on a chromosome masking or OVERRIDING the effect of a DIFFERENT VARIANT of the same gene. (Aa –> A is dominant)

AA –> brown
Aa –> brown
aa –> orange
OBSERVABLE HUMAN CHARACTERISITICS: Rolling tongue, cleft chin, bent pinky.

Question 5

Heredity: Explain RECESSIVE gene (provide example)

Answer 5

Variation of a gene on a chromosome that will only be expressed if TWO RECESSIVE genes are present (no dominant trait is present). (aa –> no dominant gene)

AA –> brown
Aa –> brown
aa –> orange
OBSERVABLE HUMAN CHARACTERISITICS: Non-rolling tongue, no cleft chin, straight pinky.

Question 6

Cell Division (6)

Answer 6

1. The continuity of life is based on the reproduction of cells, or cell division.
2. Single-celled organism
   - -> Binary fission aka asexual reproduction.
3. Multi-celled organism
   - -> Cells in bone marrow make new red blood cells.
4. Most cell division involves the distribution of IDENTICAL GENETIC MATERIAL to two daughter cells.
5. The molecule DEOXYRIBONUCLEIC ACID (DNA) contains our genetic information.
6. A cell’s DNA must be copied before the cell can divide - this ensures the daughter cell each ends up with a complete genome.

Question 7

What is a GENOME?

Answer 7

The COMPLETE set of GENETIC MATERIAL of an organism or virus.

It provides all of the INFORMATION the organism requires to FUNCTION. In living organisms, the genome is stored in long molecules of DNA called chromosomes.

Question 8

What is a GENE?

Answer 8

A segment of DNA molecule that codes for a particular trait.
–> A gene is a portion of a DNA molecule that carries information (code) that helps to produce a particular trait of an organism (hair, skin, eyes, etc.)

Question 9

What is a LOCUS?

Answer 9

The location of a gene on a chromosome.
–> Each gene occupies a specific location, or locus, on a chromosome.
For all cells, it is the same placement, however the coding varies
from person to person.

Question 10

What is the difference between CHROMATIN and CHROMOSOME?

Include Sister chromatids and centromere

Answer 10

CHROMATIN:
A mass of thread-like strands of DNA. When a cell is NOT dividing, DNA is in the form of long, thin chromatin fibres in a RELAXED STATE.

CHROMOSOME:
Cellular structures containing a very long DNA molecule and associated PROTEINS that are COMPRESSED and packed.
–> Found in the NUCLEUS

SISTER CHROMATIDS:
Each duplicated chromosome has two sister chromatids. Sister chromatids are JOINED COPIES of the original chromosome.

CENTROMERE:
Region on a chromatid containing specific DNA sequences where the chromatid is ATTACHED most closely to its SISTER.
–> Created by protein bound to the centromeric DNA sequence and gives the chromosome a NARROW “waist”
–> The part of the chromatid on either side of the centromere is referred to as an ARM.

Question 11

What are the 3 STAGES of the CELL CYCLE (5, 1, 3)

Answer 11

1. INTERPHASE:
2. The stage which cells are BETWEEN division, is called interphase.
3. During interphase, the cell grows and carries out its NORMAL FUNCTIONS.
4. The chromosomes in the nucleus form a mass of THRED LIKE STRUCTURE called CHROMATIN
5. The REPLICATION (s phase) of chromosomes as well as cellular components during interphase result in pairs of SISTER CHROMATIDS, each containing exactly the SAME GENES at the same LOCI.
6. Each original chromosome and its duplicate remain attached by a structure called the CENTROMERE. While attached they are referred to as sister chromatids.
7. MITOSIS:
8. Genetic material in the nucleus is DIVIDED EQUALLY into two new nuclei.
9. CYTOKINESIS:
10. Mitosis is followed immediately by cytokinesis, the stage of the cell cycle when the CYTOPLASM OF A CELL IS DIVIDED to form two new cells.
11. Although the nucleus is divided during mitosis, the division of the CELL CONTENT in two new daughter cells happens during cytokinesis.
    - -> There are two nuclei in a cell at once.
12. CLEAVAGE FURROW develops to “cut” the two cells apart.
    - -> Cell plate in plants
    - -> During the growth stage of the cell cycle, additional copies of organelles are formed.

Question 12

More about INTERPHASE + purpose (4)

Answer 12

1. G1 - beginning of cell growth.
2. S - DNA is synthesized and duplicates.
3. G2 - Cell undergoes its FUNCTIONS (growing + producing proteins)

–> Purpose: Replenish dead or dying cells, to allow an organism to grow and develop.

Question 13

What are the CHECKPOINTS intended for? (2)

Answer 13

1. Regulatory points at which the cell examines internal and external cues and decides whether or not to move forward with division (security check if there are ant issues with the cell)
2. The spindle checkpoint: at the transition from metaphase to anaphase.

Question 14

G1 CHECKPOINT (What is it looking for) (7)

Answer 14

1. SIZE: is the cell large enough to divide?
2. NUTRITION: Are all the needed nutrients present in the environment?
3. MOLECULAR SIGNALS: Is the cell receiving positive cues (such as growth factors) from its neighbours.
4. MECHANICAL SIGNALS: Is the cell attached to a support? Is it crowded by neighbours.
5. DNA INTEGRITY: Is any of the DNA damaged?
6. If the cell does not pass G1 checkpoint, it may enter G0 resting phase –> in order to be fixed or to die.
7. Once cell passes G1, it is committed to divide.

Question 15

G0 phase (3)

Answer 15

1. Resting phase
   - -> Nerve cells in the brain stop dividing when the brain is developed and cannot reenter the cell cycle (CANNOT GO BACK INTO G1)
2. Liver cells can be in G0 but re-enter the cell cycle if the liver is damaged or needs repair (stays in G0 until ready to be sent back)

Question 16

G3 phase (7)

Answer 16

1. After S phase.
2. Checks for DNA integrity: Is any of the DNA damaged?
3. DNA replication: Was the DNA completely copied during the S phase?
4. If errors or damage are detected, the cell will pause for repair.
5. If the problem is fixed, the cell will re-enter the cell cycle and divide.
6. If the damage is irreparable, however, the cell may instead under go APOPTOSIS, or PROGRAMMED CELL DEATH.
7. This ensures that damaged DNA is not passed onto daughter cells and is important in preventing cancer.

Question 17

CELL DEATH: Explain NECROSIS and APOPTOSIS

Answer 17

NECROSIS:

1. Cells may die due to external factors.
   - -> Toxins, infections, trauma

APOPTOSIS:

1. Programmed and targeted death
   - -> White blood cells divide to fight viral infections. When they are no longer required they undergo apoptosis.

Question 18

Explain the SPINDLE CHECKPOINT (6)

Answer 18

1. Happens at METAPHASE TO ANAPHASE
2. Checks for ALIGNMENT: Chromosomes are lined up at the metaphase plate.
3. Checks for ATTACHMENT: Each chromosome is attached to a spindle fibre.
4. Cells look for “straggler” chromosomes that are in the wrong place.
5. Cell will pause mitosis allowing time for spindle to capture stray chromosomes.
6. If a cell fails to pass the spindle checkpoint, it may go into apoptosis.

Question 19

PROPHASE: PREPARATION PHASE (4)

Answer 19

1. Chromatids in DNA begin to shorten and thicken and become visible under a microscope.
2. Small protein bodies in the cytoplasm called centrioles separate and move to the opposite poles of the cell.
3. The nuclear membrane also starts to dissolve.

Question 20

METAPHASE: ORGANIZATIONAL PHSAE (1)

Answer 20

1. Chromosomes line up in the middle of the cell with the help of spindle fibers attached to the centromeres of each replicated chromosome (sister chromatid)

Question 21

ANAPHASE: SEPARATION PHASE (1)

Answer 21

1. chromosomes split in the middle (detach from centromere) and sister chromatids are pulled by the spindle fibres to opposite poles of the cell.

Question 22

TELOPHASE (2)

Answer 22

1. Chromosomes reach opposite poles of the cell and begin to unwind/ relaxing. As they do so, the spindle fibers dissolve and nuclear membranes form around the chromosome.