The cell cycle and mitosis and cellular organisation Module 2

Question 1

Describe the cell cycle briefly?

Answer 1

Order:

Cell division:

M phase - Mitosis and cytokenesis

Interphase: cell growth and reproduction

G1 G1 checkpoint S G2 checkpoint

Question 2

What occurs at G1 checkpoint and G2 checkpoint?

Answer 2

G1 checkpoint: Cell checks that the chemicals required for replication are present, and for any DNA damage before entering the s Phase G2 checkpoint: The cell checks if all the DNA has been replicated without damage, to see if it can enter the M phase

Question 3

The 6 steps in cell division?

Answer 3

Interphase Prophase (Mitosis) Metaphase (Mitosis) Anaphase (Mitosis) Telophase (Mitosis) Cytokenesis

Question 4

What occurs during interphase?

Answer 4

The cell carries out normal functions, but also prepares to divide Cell’s DNA is replicated, to double it’s genetic content, the organelles are also replicated so it has spare ones ATP content is increased (provides energy for cell division)

Question 5

What’s a chromosome, a chromatid, sister chromatids, homologous pairs and a centromere?

Answer 5

A chromosome is half the X before replication in interphase, and is the whole X shape after replication A chromatid is the part of the X which would be there before replication SIster chromatids, and the bottom or top 2 parts of the X paired up Homologous pairs are when there’s 1 chromosome from the mum and 1 from the dad, they have the same genes in the same order, but will have different allels Centromere joins the 2 strands of the chromosome in the middle

Question 6

Describe what occurs in the first step of mitosis, prophase?

Answer 6

Chromosomes condense Centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called spindle Nuclear envelope breaks down and chromosomes lie free in the cytoplasm

Question 7

What occurs in the second step of mitosis, metaphase?

Answer 7

The chromosomes line up along the middle of the cell (laying sideways), and become attached to the spindle by their centromers Metaphase checkpoint, checks to see that all chromosomes are attached to the spindle before it can continue

Question 8

What occurs in anaphase, the 3rd of mitosis?

Answer 8

Centromers divide Separating each pair of sister chromatids, the spindles contract pulling the chromatids to the opposite ends of the cell

Question 9

What occurs in telophase, the 4th step of mitosis?

Answer 9

The chromatids reach the opposite poles of the spindle, and uncoil becoming long and thin again, so they’re now called chromosomes again A nuclear envelope forms around each group of chromosomes so there are now 2 nuclei Cytokenesis occurs next 9 (not part of mitosis)

Question 10

Describe cytokenesis in mitosis?

Answer 10

The cytoplasm divides, a cleavage furrow forms to divide the cell membrane Produces 2 daughter cells which are genetically identical to each other and the original cell

Question 11

Uses of mitosis?

Answer 11

Need for growth of multicellular organisms Repairing damaged tissue Method of asexual reproduction

Question 12

What occurs in sexual reproduction?

Answer 12

2 gametes (an egg and a sperm), join together at fertilisation to form a zygote

Question 13

Where does meiosis occur?

Answer 13

Occurs in sexual reproductive organs to produce gametes

Question 14

What’s a gamete and what type of cell are they?

Answer 14

Produced in sexual reproductive organs, and contain half the amount of chromosomes of a normal cell, so they are haploid cells, and are all gentically different to each other as contain different combinations of chromosomes

Question 15

How many chromosomes do human cells have?

Answer 15

46, so 23 homologous pairs

Question 16

What are the steps in meiosis?

Answer 16

Interphase (DNA replicated) Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Cytokenesis Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Cytokenesis

Question 17

What occurs in prophase 1, the first step of meiosis?

Answer 17

(DNA has already been replicated in interphase) Chromosomes condense, and arrange themselves into homologous pairs Crossing over occurs Centrioles start moving to opposite ends of the cells, forming the spindle fibres Nuclear envelope breaks down

Question 18

What occurs in metaphase 1, the second step of meiosis?

Answer 18

The homologous pairs line up across the centre of the cell, and attach to the spindle fibres by their centromers

Question 19

What happens in anaphase 1, the third step of meiosis?

Answer 19

The spindles contract, separating the homologous pairs, one chromosome goes to each end of the cell

Question 20

What occurs in telophase 1, the 4th step of meiosis?

Answer 20

Nuclear envelope forms around each group of chromosomes, and then cytokinesis occurs and 2 haploid daughter cells are produced (still double stranded)

Question 21

What happens in meiosis 2?

Answer 21

All the same steps as mitosis Produces 4 genetically different haploid daughter cells (single stranded chromosomes) = gametes

Question 22

Describe chromatids crossing over in Prophase 1?

Answer 22

Homologous pairs have come together and pair up, the chromatids twist around each other, and bits of chromatids swap over The chromosomes still contain the same genes, but have different alleles

Question 23

2 ways meiosis creates cells which are genetically different?

Answer 23

Crossing over if the chromatids Independent assortment of chromosomes

Question 24

Describe the independent assortment of chromosomes?

Answer 24

Each homologous pair of chromosomes in your cells is made up of one chromosome from your mum (maternal), and one from your dad (paternal) When the homologous pairs line up in metaphase 1, and are separated in anaphase 1, it’s random which chromosome from each pair ends up in which daughter cell So all 4 daughter cells have different combinations of maternal and paternal chromosomes

Question 25

What are stem cells?

Answer 25

Unspecialised cells, that can develop into different types of cells

Question 26

Where are stem cells most commonly found?

Answer 26

In human embryos

Question 27

What’s the process of a stem cell dividing to become a new cell which then becomes specialised?

Answer 27

Differentiation

Question 28

What do adult stem cells in the bone marrow differentiate into?

Answer 28

They divide and differentiate to replace worn out erythrocytes (red blood cells) and Nuetrophils (white blood cells)

Question 29

In plants what do the stem cells in the meristems differentiate into?

Answer 29

Xylem vessels and phloem sieve tubes

Question 30

Why could stem cells be used to cure nuerone disorders such as Alzheimers and parkinsons?

Answer 30

In Alzheimers nerve cells in the brain die in increasing numbers, resulting in memory loss. Stem cells could be used to regrow healthy nerve cells In parkinsons loss of nerve cell which produces dopamine for movement, can regrow these with nerve cells

Question 31

How are nuetrophils (type of white blood cell) adapted to perform their function?

Answer 31

Their flexible shape allows, them to ingest foreign particles or pathogens. The lysosomes in their cytoplasm contain digestive enzymes to break down the engulfed particles

Question 32

How are erythrocytes adapted to perform their function?

Answer 32

The bioconcave disc shape provides a large surface area for gas exchange They have no nucleus, so there’s more for haemoglobin

Question 33

How are epithelial cells (cover the surfaces of organs) adapted to perform their function?

Answer 33

CIliated epithial cells (in the air ways) have cilia that beat to move particles away Squamous epithelial cells (in the lungs) are very thin to allow efficent diffusion of gases

Question 34

How are sperm cells adapted to perform their function?

Answer 34

Have a flagellum so they can swim to the egg Have lots of mitochondrion to provide energy to swim The acrosome (head) contains digestive enzymes, that enable the sperm to penetrate the surface of the egg

Question 35

How are palisade mesophyll cells in leaves adapted to perform their function?

Answer 35

They do most of the photosynthesis, so they contain many chloroplasts, so can absorb a lot of sunlight The walls are thin, so CO2 can easily into the cell

Question 36

How are root hair cells adapted to their perform their function?

Answer 36

Absorb mineral ions from the soil, so have a large surface area for absorption, and a thin permeable cell wall for entry of water and ions The cytoplasm contains extra mitochondria to provide the energy required for active transport

Question 37

How are guard cells adapted to perform their function?

Answer 37

Found in pairs with a gap between them to form a stoma, which is a tiny pore in the surface of the leaf used for gas exchange In the light, guard cells take up water and become turgid, forcing them open, and allowing gas exchange for photosynthesis

Question 38

What’s a tissue?

Answer 38

A group of cells that are specialised to work together to perform a particular function

Question 39

What does the tissue squamous epithelium do?

Answer 39

A single layer of flat cells lining a surface, found in the alveoli of the lungs

Question 40

What does the tissue ciliated epithelium do?

Answer 40

Layer of cells covered in cilia, it’s found on the surfaces where things need to be moved, eg in the trachea to move mucus

Question 41

What do muscle tissues do and what does it consist of?

Answer 41

Made up of muscle fibres, there are 3 types of muscle tissue, smooth (found in lining of stomach wall), cardiac (found in heart), and skeletal which is used to move

Question 42

What does the tissue cartilage do?

Answer 42

Type of connective tissue found in the joints Formed when cells called chondrolasts secrete an extracellular matrix in which they become trapped in

Question 43

What does xylem tissue do?

Answer 43

Transports water around the plant Supports the plant Contains dead hollow xylem vessel cells and living parenchyma cells

Question 44

What’s an organ?

Answer 44

Group of different tissues that work together to perform a particular function Eg. the lungs and leaves

Question 45

What’s an organ system?

Answer 45

Organs working together to perform a particular function, eg. respiratory system or circulatory system

Question 46

What does phloem tissue do?

Answer 46

Transports sugars around the plant, arranged in tubes made up of sieve tube elements and companion cells