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GCSE - Biology > Cell Division + Reprduction AND dna + Inhertiance > Flashcards

Cell Division + Reprduction AND dna + Inhertiance Flashcards

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1
Q

4.1.2.1

Where are chromosomes found?

A

Nucleus

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2
Q

4.1.2.1

What are chromosomes made of?

A

DNA molecules

Each chromosome carries a large number of genes

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3
Q

4.1.2.1

What are chromosomes usually found in?

A

Pairs

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4
Q

4.6.1.8

How many chromosome PAIRS does an ordinary human body contain?

A

23 pairs of chromosomes

46 chromosomes

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5
Q

4.6.1.8

What determines sex?

A

One of pair of the chromosome carry the genes that determine sex

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6
Q

4.6.1.8

Female Sex gene arrangement?

A

XX

Homozygous

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7
Q

4.6.1.8

Male sex gene arrangement

A

XY

heterozygous

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8
Q

4.1.2.2

What’s the cell cycle (simple)?

A

Cells divide in a series of stages called the cell cycle

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9
Q

4.1.2.2

What happens to the genetic material during the cell cycle (breif)?

A

It gets doubled then that genetic material is split between 2 identical daughter cells

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10
Q

4.1.2.2

Cell cycle explained

A

Interphase - Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicated to from two copies of each chromosome.

Mitosis - In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.

Cytokinesis- Finally the cytoplasm and cell membranes divide to form 2 identical cells.

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11
Q

4.1.2.2

Why is mitosis important?

A

Cell division by mitosis is important in the growth and development of multicellular organisms.

Eg. Skin cells divide by mitosis as they need to be continually replaced

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12
Q

4.1.2.2

What type of daughter cells are produces in mitosis?

A

2 genetically identical daughter cells

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13
Q

4.6.1.2
Where does meiosis take place
How is it different in terms of chromosomes to mitosis?

A

Meiosis takes place in the reproductive organs of animals + plants and it results in the production of sex cells called gametes, with only half the original chromosomes. They’re therefore called haploid cells.

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14
Q

4.6.1.1

What are the sex cells in animals?

A

Egg (ovary)

Sperm (testes)

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15
Q

4.6.1.1

What are the sex cells in plants?

A

In flowering plants:

Ovum (egg)
Pollen

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16
Q

4.6.1.2

Describe meiosis

A

Cells in the reproductive organs divide by meiosis

Copies of genetic information are made. The cell divides TWICE to from four gametes, each with a single set of chromosomes. All the gametes are genetically different from eachother + the parents.

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17
Q

4.6.1.2

What happens to the gametes at fertilisation?

A

Gametes join at fertilisation to restore the normal number of chromosomes (46). The new cell divides by MITOSIS. The number of cells increases.
As the embryo develops cells differentiate

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18
Q

4.6.1.1

Sexual reproduction

A

There is a mixing of genetic information which leads to variety in the offspring.
The formation of gametes involves MEIOSIS

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19
Q

4.6.1.1

Asexual reproduction

A

Involves only 1 parent and no fusion of gametes. There is no mixing of information leading to all genetically identical offspring (clones).
Only MITOSIS is involved

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20
Q

4.6.1.3

Advantages of sexual reproduction

A

Produces variation in the offspring.

If the environment changes variation gives survival advantage by natural selection.

Natural selection can be speeded up by humans in selective breeding to increase food production

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21
Q

4.6.1.3

Advantages of A-sexual production

A

Only one parent needed

More time and energy efficient as you don’t need to find a mate

Faster than sexual production

May identical offspring can be produces when conditions are favourae.

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22
Q

4.6.1.3

Give some examples of where organisms reproduce by both methods depending on the circumstances

A

Malarial parasites reproduce asexually in the human host but sexually in the mosquito

Many fungi reproduce asexually by spores but also sexually to give variation

Many plants produce seeds sexually but also reproduce asexually by runners such as strawberry plants or bulb divisor such as daffodils

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23
Q

4.6.1.4

What’s the nucleus made of?

A

chemical called DNA

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24
Q

4.6.1.4

What’s the DNA structure?

A

DNA is a polymer made up of 2 stranded forming a double helix.

25
Q

1.6.1.4

What he DNA structure contained in?

A

chromosomes

26
Q

4.6.1.4

What’s a gene?

A

A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.

27
Q

4.6.1.4

What’s a genome?

A

The genome of an organism is the entire genetic material of that organism. The whole human genome has now been studies and this will have great importance for medicine in the future.

28
Q

4.6.1.4

Why’s it important to understand the human genome?

A

Search for genes linked to different types of disease
Provide better treatment for genetic disorders
Use in tracing human mitigation patterns from the past

29
Q

4.6.1.5

What are the 4 bases?

A

A - adenine
C - cytosine
G - guanine
T - thymine

Complimentary strands:
A and T
C and G

30
Q

4.6.1.5

What are the DNA polymers made of?

A

The DNA polymer is made up of repeating g nucleotides. Each nucleotide consists of a common sugar and phosphate group with 1 of 4 bases attached to the deoxyribose sugar

The long strands of DNA consist of alternating sugar phosphate sections. Attached to each deoxyribose sugar if 1 of 4 bases.

(Learn diagram)

31
Q

4.6.1.5

How many bases are needed to code for 1 amino acid?

A

3 bases code for 1 amino acid

32
Q

4.6.1.5

Why’s the order of bases important for the amino acid being coded?

A

The order of the bases control the order in which the amino acid are assembles in to form a particular protein

A difference in bases can cause a different order of amino acids causing a different shaped protein causing a different active site shape causing the enzyme to not be able to carry out its function (correctly)

33
Q

4.6.1.5

What is the DNA polymer made up of?

A

Repeating nucleotide units

34
Q

4.6.1.5

Describe protein synthesis

A

When a particular protein is required, the section of DNA forming the gene is copied by making a template. This is a molecule called messenger RNA (mRNA). As only the code for one gene, and not the whole DNA has been copied it is small enough to travel outside the nucleus. It binds to a ribosome which is where the pricing will be made. The order of bases on the mRNA is read in groups of three letters by the ribosome. Each triplet is then used by the ribosome to guide the correct amino acid into place. The amino acids are carried to the ribosome by carrier molecules called transfer RNA (tRNA). Each tRNA carries only one specific amino acid. When the protein chain is complete and folds up to form a unique shape. This unique shape enables the proteins to do their job as enzymes, hormones or forming structures in the body such as collagen.

35
Q

4.6.1.5

Describe how variants may influence the phenotype?

A

Not all parts of DNA code for proteins. Non-coding parts of DNA can switch genes on and off, so variation in these area of DNA may affect how these genes are expressed

36
Q

4.6.1.5

Where are proteins synthesised?

A

Proteins are synthesised on ribosomes, according to a template. Carrier molecules bring specific amino acids to add to the growing protein chain in the correct order.

The order of bases on the mRNA is read in groups of three letters by the ribosome. Each triplet is then used by the ribosome to guide the correct amino acid into place. The amino acids are carried to the ribosome by carrier molecules called transfer RNA (tRNA). Each tRNA carries only one specific amino acid.

37
Q

4.6.1.5

What happens to the protein chain when it’s complete?

A

It folds up to form a unique shape. This unique shape enables the proteins to do their job as enzymes,hormones or forming structures in the body such as collagen

38
Q

4.6.1.5
Do mutations occur constantly?
Why / why is it not a problem?

A

Mutations occur continuously. Most do not alter the protein or on,y alter it slightly so that it’s appearance or function isn’t changed.

A few mutations code for an altered protein with a different shape. An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.

39
Q

4.6.3.3

Describe the development of our understand of genetics including the work of Mendel

A

In the mid-19th century Gregor Mendel carried out breeding experiments on plants. One of his observation was that the inheritance of each characteristic is determined by “units” that are passed in the defendants unchanged. In the late 19th century behaviour of chromosomes was observed.

In the early 20th century it was observed that chromosomes and Mendels “units” behaved in similar ways. This lead to the idea that the “units” (now called genes) were located on chromosomes.

In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out.

This scientific work by many scientists led to the gene theory being developed

40
Q

4.6.3.3

Why was the work of Mendel’s discovery not recognised until after his death?

A

Because he wasn’t a scientist

He wasn’t able to explain his work, there was no knowledge about genes at the time

Didn’t publish his work

41
Q

4.6.1.6

What is a gamete?

A

Gametes are the female and male sex cells

eggs and sperm

42
Q

4.6.1.6

What’s a chromosome

A

Chromosomes are thin strands of DNA

43
Q

4.6.1.6

What’s a gene?

A

A gene is a small section of DNA on a chromosome that codes for a particular sequence of amino acids, to make a specific protein.

44
Q

4.6.1.6

What’s an allele?

A

Alleles are different versions of the same gene.

45
Q

4.6.1.6

What does dominant allele mean?

A

A dominant allele is always expressed, even if one copy is present. Dominant alleles are represented by a capital letter, for example, A.

The allele masking the recessive gene

46
Q

4.6.1.6

What does recessive allele mean?

A

A recessive allele is only expressed if the individual has two copies of it and does not have the dominant allele of that gene.

The allele that is masked by the dominate gene

47
Q

4.6.1.6

What does homozygous mean?

A

Homozygous alleles are both identical for the same characteristic, for example AA or aa.

48
Q

4.6.1.6

What does heterozygous mean?

A

Heterozygous alleles are both different for the same characteristic, for example Aa.

49
Q

4.6.1.6

What does genotype mean?

A

The genotype is the collection of alleles that determine characteristics and can be expressed as a phenotype.

Make up of the gene

50
Q

4.6.1.6

What does phenotype mean?

A

Phenotype is the physical expression of the genotype

51
Q

4.6.1.6
Can some characteristics be controlled by a single gene?
If so give an example

A

Some characterises are controlled by a single gene such as:
Fur colour in mice
Red and green colour blindness in humans

Each gene may have different forms called alleles

52
Q

4.6.1.6

At what level do the alleles / genotypes operate at?

A

Molecular level to develop characteristics that can be expressed as a phenotype.

53
Q

4.6.1.6

What are most characteristics a result of?

A

Multiple genres interacting rather than a single gene

54
Q

4.6.1.7

What’s an inherited disorder caused by?

A

Caused by the inheritance of certain alleles

55
Q

4.6.1.7

Give an example of an inherited disorder caused by a dominant allele

A

Polydactyl (having extra fingers / toes)

Doesn’t shorten life expectancy

56
Q

4.6.1.7

Give an example of an inherited disorder caused by a recessive allele

A

Cystic fibrosis (a disorder of cell membranes)

Cystic Fibrosis is an autosomal recessive disorder
Symptoms - excesses mucus being produces in the linings, difficulty breathing, difficulty digesting foods (proteins and fats), life expectancy of around 40years

57
Q

4.6.1.7

Embryo screening positives

A

Allows you to identify foetuses with genetic disorders during early pregnancy and potentially provide better treatment for the child (options for treatment)

Financial consideration - can the family afford to provide suitabile treatment for the baby with a genetic disorder

NHS - fewer patients with genetic disorders

Quality of life

Allows parents to make a choice allows them to be prepared

ONLY IVF Can only implant a healthy embryo that doesn’t have the genetic disorder which removed other worries of the parent

58
Q

4.6.1.7

Embryo screening negatives

A

Can lead to people picking what type of child they want (build a baby)
- Can lead to ethical issues

Against some religeous veiws (to abort the child as it was gods plan or to be against the medical treatment)

Veiws against abortion
Finding out late in pregnancy - too late to abort the child? (Any pregnancy can be aborted as long as 2 doctors sign it off - 24weeks) (some genetic disorders can be aborted after 24weeks)

False negatives / false positives - never 100% accurate
False neg - baby born with genetic disorder
False pos - abort healthy baby

ONLY Embryos from IVF - what’s done with them

AMNIO + CVS ONLY Increased risk of Miscarriages
Side effects - discomfort and pain

GCSE - Biology (13 decks)

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