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Biology > B2 + B13 - Cell Division And Reproduction > Flashcards

B2 + B13 - Cell Division And Reproduction Flashcards

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1
Q

Mitosis

A

When a cell reproduces itself by splitting to form two identical offspring

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2
Q

Process of mitosis

A

The DNA replicates to make a copy of itself, forming an ‘X’ shaped chromosome

The chromosomes line up in the middle of the cell

Each arm of the chromosome gets pulled to opposite sides of the cell

The cytoplasm and cell membrane divide to form 2 identical daughter cells

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3
Q

Meiosis

A

Produces cells which have half the normal number of chromosomes (23)

Only happens in reproductive organs where gametes are made

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4
Q

Process of meiosis

A

The DNA replicates to make a copy of itself, forming an ‘X’ shaped chromosome

The chromosomes line up in the middle of the cell

Each pair of chromosome gets pulled to opposite sides of the cell, so each new cell only has one copy of each chromosome

They then line up in the middle of the cell again

Each arm of the chromosome gets pulled to opposite sides of the cell

This creates four different gametes with 23 chromosomes

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5
Q

Stem cells

A

Unspecialized cells capable of developing into many
different types of cell (not all)

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6
Q

Embryonic stem cells

A

Develop into all the different types of cell in the body

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7
Q

Stem cells becoming specialised

A

A stem cell starts to divide into a stem cell and a tissue

The tissue then divides further becoming more and more specialised

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8
Q

Cell division in plants

A

Cell division occurs in the meristem of a plant

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9
Q

Therapuatic cloning

A

Produces stem cells with the same genetic make-up as the patient

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10
Q

Process of therapeutic cloning

A

The nucleus from a human egg cell is discarded

The cell from a patient has its nucleus removed and placed into the donor egg cell

The cell is stimulated to divide, developing an embryo

After 4-5 days the stem cells are removed

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11
Q

Advantages of embryonic stem cells

A

The stem cells produced aren’t rejected by the patients body

They divide and grow rapidly

Can create a wider variety of cells

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12
Q

Disadvantages of embryonic stem cells

A

Can kill the embryo, unethical

Expensive to research and develop

Higher risk of cancer or tumors

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13
Q

Advantages of asexual reproduction

A

Only one parent is needed - saves time and energy finding a mate

Can produce large numbers of identical offspring

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14
Q

Disadvantages of asexual reproduction

A

No variation could cause an entire population to be wiped out if the environment changes

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15
Q

Advantages of sexual reproduction

A

Variation in offspring means less susceptible to environmental change

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16
Q

Disadvantages of sexual reproduction

A

Time and energy needed to find a mate

Time and energy needed to spread gametes

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17
Q

Sexual reproduction in plants

A

Flowering plants use sexual reproduction

Pollen is moved from one flower to another by the
wind or by insects like bees

When pollen reaches the new flower, it travels to the ovary where it joins with egg cells (ovules) to make seeds

The seeds are scattered by animals or the wind, this process is called dispersal

Some of the seeds will germinate and grow into new plants

18
Q

Asexual reproduction in plants

A

Strawberries produce runners through specially directed mitosis that are identical to themselves

19
Q

DNA

A

The genetic code which makes up genes

20
Q

Polymer

A

A long molecule made up of repeating units

21
Q

DNA bases

A

Adenine (A) - - - - Thymine (T)

Cytosine (C) - - - - Guanine (G)

22
Q

Triplet code

A

A group of three bases coding for a specific amino acid

23
Q

Genome

A

The entire genetic material of an organism

24
Q

Process of protein synthesis

A

The DNA is unzipped and a mRNA (an exact copy of the DNA) binds to each codon (three bases)

This is known as transcription

The mRNA chain moves out of the nucleus into the cytoplasm where it finds a ribosome

tRNA binds to the mRNA and also to amino acids floating in the cytoplasm

Once tRNA joins each mRNA the amino acids join together through bonds created by enzymes

This creates a chain of amino acids known as polypeptides

25
Q

Mutation

A

A change in the base sequence in a strand of DNA

26
Q

Three types of mutation

A

Substitution

Addition

Subtraction

27
Q

Effects of mutations

A

They may have no affect at all on the protein formed

They may alter the proteins appearance slightly but not enough to alter its function

They may change the amino acids coded for and may change the shape of the protein – this could result in it being no longer able to function

They may be advantageous e.g. result in a more efficient enzyme

28
Q

Allele

A

Different forms of the same gene

29
Q

Dominant allele

A

Represented by a capital letter

30
Q

Recessive allele

A

Represented by a lower case letter

31
Q

Homozygous dominant

A

Both allele’s are dominant

32
Q

Homozygous recessive

A

Both allele’s are recessive

33
Q

Heterozygous

A

Two different allele’s

34
Q

Genotype

A

The genetic make-up of an organism

35
Q

Phenotype

A

An individuals observable traits

36
Q

Polydactyl

A

Inherited condition in which a person has extra fingers or toes

It is caused by a dominant allele of a gene

37
Q

Huntington’s disease

A

Inherited disorder that affects the nervous system

It is caused by a dominant allele

38
Q

Cystic fibrosis

A

Inherited condition that causes sticky mucus to build up in your lungs and digestive system

It is caused by a recessive allele

39
Q

Amniocentesis

A

A test to see whether your child could grow up with genetic disorders

Carried out 15-16 weeks before pregnancy

A needle is inserted through the skin

40
Q

Chronic villus sampling

A

A test to see whether your child could grow up with genetic disorders

Carried out 10-12 weeks before pregnancy

A catheter (long tube) is inserted through the the cervix

41
Q

Advantages of embryonic screening

A

Checks for genetic disorders

Can be used for women over 35

Can help plan child’s future

42
Q

Disadvantages of embryonic screening

A

May go against religion

Small risk of miscarriage

Needs experienced doctor

Biology (12 decks)

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