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Elias - ALEVEL > Alevel Biology Topic 3 > Flashcards

Alevel Biology Topic 3 Flashcards

1
Q

General features of a Prokaryote?

A
  • Have no membrane-bound organelles
  • Unicellular (Single-celled)
  • No nucleus
  • Circular DNA
  • DNA not associated with histone proteins
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2
Q

Features of a Bacteria cell (Prokaryote)

A
  • Ribosome
  • Plasmid
  • Pili
  • Nucleoid
  • Cell surface membrane
  • Cell wall
  • Flagellum
  • Capsule
  • Cytoplasm
    -mesosomes
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3
Q

Role of plasmid

A

-Plasmid is a Double stranded DNA which often contains additional genes that aid bacterium’s survival, such as toxin producing genes)

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4
Q

Role of pili

A

Thin, protein tubes, which allow bacteria to stick to surfaces. Not found on all bacteria

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5
Q

Nucleoid

A

Single circular length DNA, carrying all the essential information. The DNA is folded in a region known as the Nucleoid

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6
Q

Cell wall

A

In all bacteria, the wall is made of peptidogylcan. This is a polymer made from sugar and amino acids

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7
Q

Flagellum

A

A whip-like structure which helps in movement and can be a sensory structure. Not found in all bacteria

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8
Q

Ribosomes in Prokaryotes

A

In prokaryotes, the ribosomes are size 70S made up from 30S and 50S subunits

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9
Q

General features of Eukaryotes?

A
  • Contains a nucleus
  • DNA that is linear and associated with histone proteins
  • Compartments within the eukaryotes cell such as vesicles that constrain enzymes, toxins, or waste products
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10
Q

Mitrocondria

A

Surrounded by a double membrane folding to form finger like projections called Cristae. Contains DNA and 70S ribosomes. Site of respiration.

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11
Q

Rough Endoplasmic reticulum

A

A series of a single, flattened sacs enclosed by a membrane. Ribosomes on the surface create proteins here

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12
Q

Capsule

A

Slimy layer on surface for protection and prevent dehydration

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13
Q

Centrioles

A

A ring of microtubules involved in the formation of the spindle fibers for cell division and transport within the cytoplasm

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14
Q

Nucleus

A

Made from a nuclear envelope containing pores. Contains Chromosomes that control the synthesis of proteins and a nucleolus

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15
Q

Nucleolus

A

A body within the nucleus where ribosomes are made

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16
Q

Ribosomes

A

The site of protein synthesis in the cytoplasm or Rough ER

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17
Q

Smooth endoplasmic reticulum

A

A system of membrane bound, flattened sacs that make lipids and steroids.

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18
Q

Golgi apparatus

A

Modification of proteins and packages them in the many surrounding secretory vesicles for transportation. They can also remove water from proteins to concentrate them. Also, carbohydrates can be added or other various substances.

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19
Q

Ribosomes in Eukaryotes

A

80S ribosomes and larger than those in prokaryotes

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20
Q

Lysosomes and how they work?

A

Single membrane sacs containing digestive enzymes involved in the breakdown of unwanted substances, or the whole cell during apoptosis. After enzymes destruct unwanted substances, the lysozyme (a vesicle essentially) fuses with the cell membrane and its contents are released through exocytosis.

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21
Q

How does an egg cell move from the ovaries to the uterus?

A

It is wafted along one of the oviducts by Ciliated cells lining the tube, and also muscle contractions.

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22
Q

What is the acrosome reaction?

A

Sperm are attracted by the chemicals released from the ovum. The acrosome in the head of the sperm swells, fuses with the sperm cell surface membrane and releases digestive enzymes. These break down the follicle cells and zona pellucida of the ovum.

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23
Q

What is the cortical reaction?

A

The sperm fuses with and penetrates the membrane surrounding egg, enzymes released by cortical granules vesicles, which fused with the ovum cell membrane, causes the zona pellucida to thicken preventing any further sperm entering the egg

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24
Q

What does the fusion of gamates to produce a fertilized egg called?

A

Zygote

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25
Q

Features of an egg cell?

A
  • Follicle cells
  • Cytoplasm
  • Haploid nucleus
  • Jelly coating (Zona Pellicula)
  • Lipid droplets
  • cell surface membrane
  • Cortical granules
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26
Q

Features of a sperm cell

A
  • Flagellum
  • acrosome
  • Mitrocondria
  • Haploid nucleus
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27
Q

Haploid number

A

n

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28
Q

Diploid number

A

2n

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29
Q

Mitosis vs meiosis

A

Mitosis is a type of cell division that produces 2 genetically identical diploid daughter cells whereas meiosis produces 4 genetically variant haploid daughter cells

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30
Q

What ways can meiosis result in genetic variation?

A
  • Independent assortment
  • crossing over
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31
Q

Why may the cortical reaction be beneficial?

A

This mechanism is advantageous because there is a higher chance of survival for a mother to be impregnated with one than two offspring.

32
Q

What is a gene?

A

A segment of DNA that codes for the synthesis of polypeptides

33
Q

What is apoptosis?

A

Programmed cell death

34
Q

What is the genome?

A

A term used to denote the entire DNA sequence of a person

35
Q

What is the locus?

A

The position of a gene on a chromosome

36
Q

What is independent assortment and how does it lead to variation?

A

The order in which chromosome pairs line up during meiosis. Explain….
An organism with 6 chromosome or 3 pairs can form eight combinations (2^3)
This leads too different combinations of chromosomes when they line up across the equator of the cell.

37
Q

What is crossing over and how does it lead to variation?

A

Homologous chromosomes come together as pairs and all four chromatids come into contact. At the point of contact, the chaisma, chromatids break and rejoin to form variation. This leads to a different combination of alleles in the chromosomes and leads variation. In METAPHASE. This does not happen in sex chromosomes

Exchange of genetic material

38
Q

What is the cleavage called in cell division?

A

Cleavage phorum

39
Q

What is the two pairs of chromosomes called togther when attached at the chiasma

A

A bivalent

40
Q

Steps of interphase:

A

G1 - cell growth
S phase - DNA replication
G2 - preparation for Mitosis

41
Q

What are the four ways of variance in general?

A

Independent assortment
Crossing over
Fertilization (sperm cell reaching)
Mutations

42
Q

What is the principle of linkage?

A

Any two genes with a locus on the same chromosome are linked together and will tend to be passed as a pair to the same gamete. Crossing over can prevent this

43
Q

What is sex linkage?

A

All the genes on the sex chromosomes are passed on with those that determine sex, these are sex linked.

44
Q

Explain sex linkage disorders

A

The genes loci for a specific disorder can be found on the X chromosome. If recessive, this means only one recessive allele is needed for the person to inherit the disorder in males XY. Two recessive alleles are need for females so have less chance of inheriting the disorder.

45
Q

Role of mitosis

A

Repair, growth, and asexual reproduction

46
Q

How does the Golgi apparatus play a role in the formation of extra cellular enzymes?

A

Vesicles enter the Golgi apparatus where they are Modified packaged into secretory vesicles which pinch from the membrane to fuse with the cell membrane in exocytosis.

47
Q

Mesosomes

A

Inward folds in the membrane of bacteria which are used for respiration

48
Q

CPAC 3 Mitosis

A
  • Warm garlic clove HCL in water bath to 55 (Breaks down the pectins that holds the cell together)
  • Cut 5mm length of garlic roots place in acetic orcein.(roots are used for meristem where cell division is frequent, the acetic will stain the chromosome dark red and fix the cells to stop mitosis)
  • Place again garlic in vial in water bath to intensify the stain
  • macerate the cells (To spread them out to appear more visible)
  • prepare a slide and examine under microscope, drawing what is visible
49
Q

Explain early embryonic development.

A

After a human zygote has undergone three complete cycles, it consists of eight cells. These are Totipotent. After 5 days, a hollow ball of cells is formed called a blastocyst. The outer layer goes on to form the placenta. An inner 50 cells form tissues and are pluripotent embryonic stem cells.

50
Q

What are totipotent cells?

A

Stem cells that retain the ability to develop into a complete human being. The ability to differentiate into any type of cell including embryonic cells

51
Q

What are pluripotent cells?

A

Makes all types of cells apart from embryonic cells

52
Q

What is the name for cells that retain a certain capacity to a variety of different cell types?

A

Multipotent (Adult stem cells)

53
Q

What feature of plant cells allows them to be reproduced using plant tissue culture?

A

Totipotency

54
Q

What does Mendels peas tell us about linkage

A

That the inheritance of one pair of factors is independent of inheritance of other pairs. However now we know through linkage that this is only happening when genes are on different chromosomes

55
Q

How is DNA arranged in a Bacteria cell?

A

Large circular DNA, No histone proteins, several plasmids, and not bound by a nucleus just rather sits in the cytoplasm

56
Q

Non sex chromosomes

A

Autosomal

57
Q

What happens in Prophase?

A
  • Chromosomes condenses
  • DNA becomes visible as threads as it supercoils around histone proteins
  • Nuclear envelope/Membrane starts to breaks down
  • each set of replicated centrioles move to opposite poles of the cell and spindle fibers start to form
  • Two sister chromatids (Identical Chromatids) up at the centromere
58
Q

What happens in Metaphase?

A

-Chromosomes line up at the equator of the cell
-with spindle fibres attached to their centromeres
-Each sister chromatid is attached to a spindle fibre originating from opposite poles (Mitosis)
-Crossing over can over between non-sister chromatids and form bivalents (Meiosis)

59
Q

What happens in Anaphase?

A

-Spindle fibers contract and shorten, pulling a set of chromosomes to opposite poles of the cell
-The sister chromatids separate at the centromere

60
Q

What happens in Telephase?

A

-Spindle fibers begin to break down by enzymes in lysosomes
-The chromosomes begin to decondense
-Nucleolus reforms
-Two separate sets of chromosomes are formed.

61
Q

What happens in Cytokinesis?

A

-The cytoplasm begins to cleave forming the cleavage forrow
-the cytoplasm is divides forming two genetically identical cells

62
Q

What is the relationship between linkage, and distance separating loci of genes

A

The closer the loci of genes, the more the genes are likely to be linked

63
Q

What is the term for chromosomes from you mother, and those from your father?

A

Mother = Maternal
Father = Paternal

64
Q

How do stem cells undergo differentiation?

A

All genes in stem cells are not all active at the same time. Specialization occurs because different genes are expressed for a specific function of a cell

65
Q

What is IPS

A

Induced pluripotent stem cells,
Where selected adult cells are reprogrammed to unspecialize into stem cells. This is effective for transplants because this minimizes the risk of rejection for an own patient IPS

66
Q

How is gene expression done?

A

Transcriptional factors (Like proteins which enable the RNA to bind to the DNA promoter region) turn on specific genes on and off. In eukaryotes these factors bind to sites called ‘enhancers’ or ‘silencers’, whereas in prokaryotes they bind to a region called the promoter site. Each type of cell has different transcription factors however.

67
Q

Explain LAC Operon?

A
  • In absence of lactose, the repressor binds to the operator region of the DNA which prevents transcription from taking place.
  • In presence of lactose, lactose binds to the repressor and is released from the operator region and transcription can take place since the RNA polymerase can move from the promotor region
68
Q

What can speed up the rate of transcription?

A
  • cAMP-CAP binds to the RNA polymerase
69
Q

What is the difference between continuous and discontinuous variation?

A

Continuous has no fixed categories like height and weight, this is controlled by more than one gene and is said to be polygenic

Discontinuous is set such as blood group where there is a limiting range, this is controlled by one gene only

70
Q

What is methylation and how does it work?

A

A variation due to envoirnmental changes, DNA and histones are more tightly packed together so transcriptional factors cannot bind to the DNA and transcription cannot occur so some genes are not expressed

71
Q

What is acetylation and how does it work?

A

A variation due to envoirnmental changes, which results in loose packing of DNA so transcriptional factors can bind and genes are expressed

72
Q

How are epigenetic changes passed on?

A

Passed onto daughter cells after cell division from the parents cell.
*If a gene is active in the parent cell, it will be active in the daughter cell

73
Q

What is the name of the flattened sacs of the Golgi apparatus

A

Cisternae

74
Q

What is the name of the flattened sacs of the Golgi apparatus

A

Cisternae

75
Q

Define Polygentic

A

A polygenic trait is a characteristic, such as height or skin color, that is influenced by two or more genes.

Elias - ALEVEL (7 decks)

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