Biology-Cell diversity and diffrentiation

Put these in order of smallest to largest

Chromatin

Chromosome

Atom

Neuclotide

DNA helix

Histone

Gene

Neucleosome

Atoms

Nucleotides

Histone

Neucleosome

Gene

DNA helix

Chromatin

Chromosome

At what phase does the replication of DNA occur

EQ

S

.describe how this cell would look different if it was in interphase

Not as dark

Single dark area in the middle

EQ

Z

As didn’t get enough chromosomes

State 2 roles of mitosis in organisms

EQ

Repair

Growth

EQ

To produce many genetically identical offspring

What condenses chromosomes or chromatin?
EQ

Chromosomes condense

What should you mention in evaluate questions?

EQ

Larger sample size

Explain the role of meristem tissue in a stem

EQ

Source of unspecialised stem cells that can differentiate into other cells

Which checkpoint checks for DNA damage first?

EQ

G1 bc cells should be stopped from entering the s phase

Brm

What happens when xylem vessels are formed

Lignin impregnates the cell walls making them impermeable to water

All cytoplasm is lost

What happens when phloem is formed

Sieve tube elements become elongated and lose most of their cytoplasm

How can stem cells be used to treat a disease mark scheme answer structure

Stem cells differentiate into (cells required) so (what the cells produce) levels increase

True or false

Neutrophils undergo mutation during differentiation

False

Tue or false

Erythrocytes develop large numbers of ribosomes early in their differentiation

True

True or false

Majorit of organelles in red blood cells are broken down by hydrolysis

True

True or false

Adult stem cells are totipotent

False

Is meiosis 2 reduction division

Yes

Is mitosis reduction division

Yes

Is meiosis 1 reduction division

No

Why is blood described as a tissue not an organ

Blood is a collection of different cells that work together to perform a function not a collection of different tissues

True or false

Adult stem cells can be used as a renewing source of undifferentiated cells

True

Pluripotent definition

Cells that can differentiate into any type of cell but cannot form whole organisms

Advantage of IPSCs

No risk of rejection

Disadvantages of IPSCs

Greater risk of cancer

Explain the role of meristem tissue in a stem

Source of undifferentiated cells for growth

Name on neurological disease that can treated by stem cells

Parkinson’s

What do you call chromosomes in meiosis 1

Homologous chromosomes

What do you call chromosomes in meiosis 2

Sister chromatids separate in anaphase

Chromosomes

Chiasmata

Parts where chromatids are joining

In what condition are chromosomes visible

When they are condensed into chromosomes

Yes chromosomes

Helicase function

Unzips dna helix

Breaks hydrogen bonds between the two strands

The enzyme microtubules depolymerase breaks down spindle fibers in mitosis/Which phase of mitosis will have the highest number of active microtubules deplymerase enzymes

Telophase-spindle fibers are broken down/depolymerased during telophase

How is mitosis significant in the development of the whole organism

Mitosis can be controlled at certain points in development which will change body plans

Can microtubules be prevented form functioning and why

Yes

By a respiratory inhibitor

Which letter shows a homologous pair of chromosomes in metaphase2

A because these both have similar shapes and length

Suggest one abnormality in the cells of a tissue that has a genetic mutation stopping the metaphase checkpoint

Some cells contain an incorrect number of chromosomes

What will happen if there is a mutation in the G2

Cells should be stopped from entering the S phase and DNA damage is checked here

List all the phases of interphase in order

G1,S,G2

Don’t include G0

What is checked at G2 checkpoint

If DNA has replicated correctly

Which stage of interphase has the highest number of cells

G1

What observations would have proved that a cell had stopped dividing in the G2 checkpoint

More DNA

No visible chromosomes

How would you do this

Measure radius of the other cell adn substitute that value into the formula for the volume of a sphere

Roles of mitosis in multicellular organisms

Gametes from haploid cells

Asexual reproduction

Draw a biological drawing of the cell in metaphase

Draw a biological drawing of a cell in anaphase

Prophase-mitosis

Mark scheme answer

Chromosomes condense and become visible

Membrane breaks down

Telophase mitosis

Spindles break down

Chromatids pulled to opposite poles of cell

New cell membrane visible down center of cell

Why does a zygote undergo mitosis and not meiosis

Cell growth

Genetically identical gametes produced

Observations of a cell in prophase1

Dark area of chromosomes visible in the center

Nuclear envelope present

No nucleolus

Explain how the organisation of homologous chromosomes during metaphase 1 increases genetic variation

Independent assortment

Homologous chromosomes line up across the equator of the cell

Maternal and paternal chromosomes face either pole in either cell

What is genetic variation

Variety of alleles

How does crossover in prophase 1 produce genetic variation

Alleles swapped

Base sequence of chromosomes altered

How do haploid gametes produce genetic variation

Sperm form one cell can fertilise an egg form any other cell in the population

Hydra can have different alleles

Why does sexual reproduction occur in some organisms only in the winter

Offspring need genetic variation to survive unfavourable condition

In what phase of interphase is the enzyme helical present

S phase

What happens at one of the checkpoints if damages DNA is present

If detected at G2 checkpoint then cell cycle is halted adn cell tries to repair damage

Which stage of the cell cycle would DNA polymerase be most active

S phase

As polymerase synthesises strands of DNA

Do erythrocytes undergo mitosis

No

At which stage does the p53 gene interrupt the cell cycle to prevent the copying of damaged DNA

G1 checkpoints

Pauses cell cycle before DNA replication occurs in the S phase

Reduction division

The first stage of meiosis where a diploid parent cell divides to produce two haploid cells,

How is the second division of meiosis different from mitosis

Separating chromatids of a pair are not the same

No homologous in second division—>cross over and genetic variation

What leads to variation within a species

Independent assortment of homologous chromosomes

What happens if DNA damage is discovered at the G2 checkpoint?

Cell cycle is halted and the cell tries to repair the DNA

What divides during mitosis

Nucleus

When does the second checkpoints occur

At the end of the g2 phase

What do G1 and g2 checkpoints both check for

Damage to DNA

What stage of mitosis is shown in this image

Telophase

What would anaphase look like in mitosis in an image

V shaped chromosomes

Chromosomes would be shown separating

What would an image of a cell that was in interphase look like

Single dark area

Chromosomes wouldn’t be visible

Why are root tissues chosen to study mitosis

Cells undergo mitosis

Two similarities between prophase in mitosis and prophase 1 in meiosis

Spindle fibres appear

Chromosomes condense in prophase 1

Name two differences between prophase in mitosis and prophase 2 of meiosis

Meiosis:

Only one chromosome present form each homologous pair

-chromatids are not genetically identical

How can phloem cells be produced

Meristem tissues divide and differentiate

Difference between tissue and organ

Tissue is collection of cells

Organ is a collection of tissues

Helicase function

Unzips double helix

Breaks hydrogen bonds between two strands

Explain how errors may occur during DNA replication

Mutation so change in DNA sequence

Exposure to mutagen

What checkpoint has not worked properly as there are more chromosomes than the normal diploid number

Not all chromatids have been replicated

Chromosomes have not aligned correctly at th equator

Why is mitosis not meiosis used for asexual reproduction on plants

Produced genetically identical cells

Maintains chromosome number

Why can bacteria not reproduce asexually by mitosis

Mitosis is nuclear division and bacteria do not have a nucleus

Why do erythrocytes have to be replaces by bone marrow stem cells

Can’t undergo differentiation as have no dna

Sequence of events in cell cycle

G2

Mitosis

Cytokinesis

G1

S

Why does interphase sometimes stop

Few nucleotides

S phase stops

As less complementary bases

Role of mitosis in fragmentation

Produce many cells that are genetically identical

How does meiosis produce genetic variation in the offspring

Independent arrangement of chromosomes in metaphase 1 and 2

Crossover

When haploid cells fuse to form diploid cells are they genetically different or identical

Meiosis occurs even if haploid cells fuse to form diploid cells

Even if join still are Gentically different

Name cell x and y

X is a lymphocyte

Y is a neutrophil

What occurs in g2 phase

Exam mark scheme

Mitochondria organelle replicates

Tubulin proteins synthesis

Are there homologous pair of chromosomes in mitosis

No

Meiotic index

number of cells in mitosis divided by the total number of cells observed

What can be deduced about a cell that remains in apoptosis

Not dividing

Spends all its time in G1

28×2=56

56×2=112

112×2=224

What is the role of guard cells in photosynthesis

Water enters guard cells from neighbouring epidermal cells By osmosis

Guard cells swell

Tips bulge and the gap between the stoma enlarges

Photosynthesis

• Light energy used to make ATP

• ATP actively transports potassium ions from epidermal cells into guard cells lowering their water potential

• Guard cells bit -on another flashcard

• Stomata opens air can enter the spaces within the layer of cells beneath the palisade cells

• Gas exchange occurs-CO2 diffuses into the palisade cells -maintains steep concentration gradient

• Oxygen produced can diffuse out of palisade cells into air spaces and out through the stomata