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Biology > 2: Meiosis Plants > Flashcards

2: Meiosis Plants Flashcards

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1
Q

What is a hermaphrodite

A

A flower which makes both male and female gametes

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2
Q

What are the female flower parts

A

Carpel: stigma, style, ovary, ovule

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3
Q

What are the make parts of the flower

A

Stamen: anther, filament.

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4
Q

Parts of the flower which aren’t to do with gametes

A

Petals, speak, nectary, receptacle, stalk

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5
Q

Where are the male gametes found

A

Inside the pollen grains.

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6
Q

What is a pollen grain

A

Where male gametes are found. Contains 2haploid nuclei, one is called the tube nucleus and the other is the generative nucleus, which will form the male gametes. It has an exine waterproof layer, the intine, cell surface membrane and a pit.

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7
Q

What are the ovules

A

They are inside the ovaries. And are the female gametes. Each ovule contains a structure called an embryo sac. Contains 6 haploid cells and one diploid cell.
It has 3 one end- the egg cell. One in the middle-primary endosperm nucleus. And 3 the other end- antipodal cells

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8
Q

Structure of an ovary

A

Ovary wall, ovule, funicle at the bottom

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9
Q

What are gametes

A

Haploid number of chromosomes, in specialised cells called gametes.

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10
Q

What is polyploidy?

A

Fish can be polyploidy. 4 sets of chromosomes.

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11
Q

What are the characteristics of the male gametes?

A

Many, mini, motile

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12
Q

What are the characteristics of the female gametes

A

Few, fat, fixed

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13
Q

what is meiosis?

A

Chromosome number has to be halved. Reduction division ad it occurs only in the sex organs.

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14
Q

What happens to the chromosomes during meiosis?

A

2 nuclear divisions resulting in 4 haploid daughter cells, with its own unique combinations to genetic material. Replicate while in interphase and onc the cells have everything they end, they enter meiosis.

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15
Q

What are the differences of mitosis and meiosis?

A

Meiosis: 2 chromosomes of each pair, homologous pairs, stay close together and result in crossing over, or recombination.
Centromeres don’t split during first division, so pairs of chromatids go to opposite ends. Then the second division takes place like mitosis, with no more replication.

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16
Q

What occurs in prophase 1

A

Each chromosome appears in condensed form with 2 chromatids. Homologous pars of chromosomes associate with each other.
Crossing over occurs

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17
Q

What occurs in metaphase 1

A

The spindle form and the pairs of chromosomes line up on the metaphase plate

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18
Q

What occurs in anaphase 1

A

Centromeres don’t divide. Once chromosome (2 chromatids) from each homologous pair move to each end of the cell

19
Q

What occurs in telophase 1

A

Nuclear membrane re forms and cells begin to divide. In some cells, it continues to full cytokinesis, in others to a prolonged interphase. NO FURTHER REPLICATIOn.

20
Q

What happens in metaphase II

A

New spindles formed and chromosomes still made up of airs of chromatids. Lined up along plate

21
Q

What occurs in anaphase II

A

The centromeres now divide ad the chromatids move to opposite ends of the cell

22
Q

What happens in telophase II

A

Nuclear envelope re-forms, the chromosomes return to their interphase state and cytokinesis occurs, vying 4 daughter cells with half the chromosome number

23
Q

What is the importance of meiosis?

A

Reduces the chromosomes number i gametes from 4 diploid to haploid, so sexual reproduction is available.
Introduces new genetic variation in 2 ways: crossing over, and random assortment

24
Q

What is random assortment?

A

The chromosomes that came from individuals 2 parts are distributed into the gametes and so into their offspring completely at random.
Eg, each gamete you produce receives 23 chromosomes. In each new gamete, any number from none to 23 could come from either maternal or paternal chromosomes. Therefore more that 8 million potential genetic combinations

25
Q

What is crossing over?

A

Recombination.
Process takes place when large, multi enzyme complexed “cut and join” bits of the maternal and paternal chromatids together. Point where the chromatids breaks in the CHIASMATA. Leads to genetic variation in its own right.

26
Q

Other than random assortment and crossing over, what else causes genetic variation?

A

Errors which are caused by mutation.

27
Q

What is the most common form of mutation?

A

translocation

28
Q

What are chromosome mutations?

A

When areas of the chromosome break off and become reattached in the wrong place

29
Q

What is translocation?

A

When a piece from one pair of homologous chromosomes breaks off and reattached itself to a completely different pair of chromosomes

30
Q

Why can. Translocation sometimes be balanced?

A

If a piece is effectively swapped between 2 different chromosomes. often healthy

31
Q

How can translocations be unbalanced?

A

If one chromosomes loses a piece and another gains it, these cause big changes to the phenotype of the individual.

32
Q

What is a mutation like?

A

Like changing a whole word. A point or gene mutation is like changing a letter. A chromosome mutation i removing or changing a whole word. It wont mean the same

33
Q

What are severe examples of translocation?

A

Translocation between chromosome 8 and 21 can result in blood cancer, known as core binding factor acute myeloid leukaemia.
Chromosome between 8 and 14 can cause Burkitts lymphoma, a cancer o white blood cells.

34
Q

What is non disjunction?

A

Occurs when a member of a pair of chromosomes ail to separate during the reduction division of meiosis, resulting in 1 gamete with 2 copies of a chromosome and 1 with none.

35
Q

What is polysomy?

A

When a cell contains 3 or more rather than 2 chromosomes of a particular type

36
Q

What is monosomy?

A

When only 1 member of a pair of chromosomes is present in a cell

37
Q

What is aneuploidy?

A

When a cell contains too few or too many chromosomes

38
Q

Are aneuploids fatal?

A

Most are, and affected foetuses don’t develop to term. Most are stillborn, or die within the first year.

39
Q

Down’s syndrome

A

Polysomy example.
Non-disjunction of chromosomes 21 in an ovum or sperm. One of the gametes will contain 2 copies of the chromosome. After fertilisation with a normal gamete, the zygote will be polysomy. Ad contain 3 copies of chromosome 21. Babies will have Down’s syndrome. Affect both mental and physical development. Problems with heart abnormalities, learning difficulties , can be quite severe.

40
Q

Factors that affect mutation rates?

A

Mutations are relatively rare events. However, vain factors increase frequency.
Ionising radiation increases mutation rate. Certain chemicals such as mutagens also increase rate.
Increases with age of parent, ova in particular.
All of the future ova of a woman are suspended in prophase 1 of meiosis whilst the woman herself is an embryo. Ova are exposed to all chemical and radiation hazards in modern life, therefore more changes when older to increase rate.

41
Q

Turners syndrome

A

Monosomy.
Few foetuses survive with aneuploidy. However, the absence of a sex chrosomes or the presence of an extra sex chromosomes is less unusual and less life threatening. Causes fertility problems. Presence or absence of a Y chromosomes determine route for sexual development i human embryos.
An embryo with at least 1 Y chromosome will develop male characteristics. One lacking Y will develop male characteristics.
When there is non disjunction of the male chromosomes, an egg may be fertilised with NO sex chromosomes. Monosomy, therefore turners syndrome. Female. Infertile, no puberty.

42
Q

What is Kleinfelers syndrome

A

XXY, and extra X chromosome. Small estates and produce little testosterone. Little facial or body hair, may develop breast tissue. Less uncle development than usual.

43
Q

What are the sex chrosomes?

A

Females XX
Males XY

Therefore turners, with 1 X will be female
Males with XXY, are male but produce female affects

Biology (21 decks)

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