Topic 3: Voice of the Genome

Question 1

3.2 Explain the centriole

Answer 1

Every animal cell has a pair
Hollow cylinders made of microtubules
Helps with the formation of spindle fibres and transport within the cytoplasm.

Question 2

3.2/3 Explain the golgi apparatus

Answer 2

Stacks of membrane bound, flattened sacs formed by the fusion of RER vesicles.
Modifies proteins and packages them into vesicles for transport

Question 3

3.2/3 Explain the Rough and Smooth Endoplasmic Reticulum

Answer 3

Systems of interconnected membrane bound sacs. Rough endoplasmic reticulum has ribosomes attached to surface and is site of protein synthesis whereas smooth has no ribosomes and creates lipids and steroids.

Question 4

3.2 What is the lysosome

Answer 4

A single membrane sac containing digestive enzymes. Break down unwanted structures in the cell and destruction of whole unwanted cells.

Question 5

3.2 What is nucleoleous

Answer 5

The dense body inside the nucleus where ribosomes are made

Question 6

Eukaryote vs Prokaryote

Answer 6

Eukaryote has a nucleus

Question 7

3.4 What is capsule in prokaryote

Answer 7

The outermost thin layer on the surface of the prokayote

Question 8

3.4 Name 5 parts of the ultrastructure of a prokaryotic cell
(C,P,F,P,M)

Answer 8

Capsule, Pilli, Flagellum, Plasmids, Mesosomes

Question 9

80s vs 70s Ribosomes

Answer 9

80s is in eukaryote and is larger

Question 10

What is a mesosome

Answer 10

Infold in plasma membrane, site of respiration in prokaryotic cell

Question 11

Sperm cell adaptation

Answer 11

Flagellum
Many mitochondria
Acrosome - allows acrosome reaction

Question 12

Egg cell adaptations

Answer 12

Food reserves (lipid droplets and protein).
Follicle cells (protective coating)
Zona pellucida (acrosome reaction)
Cortical Granules (cortical reaction)

Question 13

3 steps of fertilisation

Answer 13

1. Acrosome reaction
2. Cortical Reaction
3. Nuclear Fusion to form zygote

Question 14

What is gene linkage

Answer 14

When genes are close together on the same chromosome, they tend to be passed together onto the same gamete - the genes are linked

Question 15

How can linked genes be seperated

Answer 15

Linked genes can be separated by crossing over

Question 16

Why does meiosis ensure genetic variation

Answer 16

Meiosis produces haploid gametes. Ensures genetic variation through independent assortment and crossing over

Question 17

What is independent assortment

Answer 17

Many different arrangements of parental chromosomes that end up in the gametes produced by meiosis. Chromosome pairs line up randomly along spindle fibers

Question 18

Crossing over

Answer 18

Exchange of chromosome segments between non-sister chromatids (not the same copy)
Genetic material rearranged as gametes contain combinations of alleles from each parent

Question 19

Cell cycle

Answer 19

IPMAT

Question 20

Parts of Interphase

Answer 20

G1 , Synthesis phase, G2

Question 21

describe prophase

Answer 21

Chromatin condenses, chromosomes become visible, nuclear membrane breaks down, nucleolus disappears, centrioles move to opposite ends of the cell in animal cells, spindle fibres form

Question 22

Describe metaphase

Answer 22

Chromosomes line up agains the cells equator, chromosome centromeres attach to spindle fibers

Question 23

Describe anaphase

Answer 23

Spindle fibers shorten - sister chromatids are pulled apart and chromosomes are pulled apart

Question 24

Describe telophase

Answer 24

Chromosomes decondense - spindle fibers break down - nuclear membranes reform around chromosomes at each pole - nucleoli reform in newly formed nuclei

Question 25

Cytokinesis in animal cells

Answer 25

Cytoskeletal fibres called contractile ring form at the centre of the cell which pinches and separates the cell

Question 26

Cytokinesis in plant cells

Answer 26

Cell plate forms in middle of cell - cell plate contains cell wall and cell membrane components, when it merges with the cell wall the cell divides

Question 27

STEM cell define

Answer 27

Unspecialised cells that can differentiate to give rise to different types of specialised cell

Question 28

Totipotent stem cells

Answer 28

An unspecialised cell which can differentiate to give rise to any cell including other totipotent cells or placental cells

Question 29

Pluripotent stem cells

Answer 29

Unspecialised cell with some genes deactivated, Less specialised than multipotent

Question 30

Multipotent stem cells

Answer 30

Unspecialised stem cells with genes deactivated moreso than pluripotent

Question 31

Advantages of stem cell use

Answer 31

Stem cells can be used to grow tissues/organs - can improve quality of life (spinal cord research) - developmental research (embryonic development)

Question 32

Disadvantages of stem cell use

Answer 32

Risk of rejection - stem cells can differentiate into cancerous cells - ethical issues

Question 33

Stem cell ethical objections

Answer 33

People may object to use of embryonic stem cells (ESCs) in research because:
Embryo destroyed after stem cells harvested - Right to life Embryo cannot consent to scientific experimentation - consent
Some people suggest induced pluripotent stem cell use (iPSCs) solves ethical concerns - embryonic and iPSCs not 100% the same - understanding required from research may only come from ESCs.

Question 34

Induced pluripotent stem cells

Answer 34

Adult somatic cells reprogrammed to be pluripotent - specific transcription factors introduced into cells to induce pluripotency

Question 35

How do stem cells differentiate

Answer 35

Unspecialised stem cell - exposed to stimulus (hormone/chemical) - only some genes activated - only activated genes transcribed - mRNA produced translated on ribosomes - proteins made - proteins made determine cell structure/function - cell permanently modified: cell differentiated

Question 36

Transcription factors

Answer 36

Transcription factors: proteins that bind to DNA and activate/ deactivate genes increasing/ decreasing the rate of transcription

Question 37

Operon definition

Answer 37

Unit of DNA containing a cluster of genes under the control of a single promoter

Question 38

LAC OPERON

Answer 38

LOOK AT BOOK

Question 39

Multicellular Organisation

Answer 39

Organelle < Cell < Tissue < Organ < Organ system < Organism

Question 40

What are epigenetic modifications

Answer 40

modifications to DNA which do not change the base sequence - they alter the activation to certain genes

Question 41

Histone definition

Answer 41

proteins that DNA wraps around to form chromatin which forms chromosomes

Question 42

Histone acetylation

Answer 42

Adds a CH3CO- group to the histone - activates chromatin - allows transcription

Loosens the DNA around histone

Question 43

Histone Methylation

Answer 43

Adds a CH3 group to the histone - deactivates chromatin - prevents transcription

Question 44

DNA methylation

Answer 44

Methyl groups added to DNA (not histones) - less transcription factors can bind - less transcription - decreased gene expression
Genes that are not transcribed have more methylation

Question 45

Polygenetic inheritance definition

Answer 45

The form of inheritance where a particular characteristic is controlled by a number of genes at many loci. Usually shows continuous variation.

Question 46

Root Tip Squah Practical Method

Answer 46

Method:
* Cut 1-2cm root tips
* Put the root tips in a watch glass with ethanol for 12 minutes
* Remove & put the root tips in a watch glass with ice cold distilled water for 5 minutes
* Remove & put the root tips into 2M HCl at 60 degrees (warmed using a water bath) for 5 minutes
* Repeat the last 3 steps
* Transfer one root tip onto a microscope slide and gently macerate the root tip with a mounted needle
* Add one drop of orcein ethnic or toluene blue stain and leave for 2 minutes
* Place a coverslip on top of the root tip squash and blot the excess stain with filter paper
* View under a microscope