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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
Features of an egg cell?
- Follicle cells - Cytoplasm - Haploid nucleus - Jelly coating (Zona Pellicula) - Lipid droplets - cell surface membrane - Cortical granules
26
Features of a sperm cell
- Flagellum - acrosome - Mitrocondria - Haploid nucleus
27
Haploid number
n
28
Diploid number
2n
29
Mitosis vs meiosis
Mitosis is a type of cell division that produces 2 genetically identical diploid daughter cells whereas meiosis produces 4 genetically variant haploid daughter cells
30
What ways can meiosis result in genetic variation?
- Independent assortment - crossing over
31
Why may the cortical reaction be beneficial?
This mechanism is advantageous because there is a higher chance of survival for a mother to be impregnated with one than two offspring.
32
What is a gene?
A segment of DNA that codes for the synthesis of polypeptides
33
What is apoptosis?
Programmed cell death
34
What is the genome?
A term used to denote the entire DNA sequence of a person
35
What is the locus?
The position of a gene on a chromosome
36
What is independent assortment and how does it lead to variation?
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
What is crossing over and how does it lead to variation?
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
What is the cleavage called in cell division?
Cleavage phorum
39
What is the two pairs of chromosomes called togther when attached at the chiasma
A bivalent
40
Steps of interphase:
G1 - cell growth S phase - DNA replication G2 - preparation for Mitosis
41
What are the four ways of variance in general?
Independent assortment Crossing over Fertilization (sperm cell reaching) Mutations
42
What is the principle of linkage?
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
What is sex linkage?
All the genes on the sex chromosomes are passed on with those that determine sex, these are sex linked.
44
Explain sex linkage disorders
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
Role of mitosis
Repair, growth, and asexual reproduction
46
How does the Golgi apparatus play a role in the formation of extra cellular enzymes?
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
Mesosomes
Inward folds in the membrane of bacteria which are used for respiration
48
CPAC 3 Mitosis
- 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
Explain early embryonic development.
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
What are totipotent cells?
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
What are pluripotent cells?
Makes all types of cells apart from embryonic cells
52
What is the name for cells that retain a certain capacity to a variety of different cell types?
Multipotent (Adult stem cells)
53
What feature of plant cells allows them to be reproduced using plant tissue culture?
Totipotency
54
What does Mendels peas tell us about linkage
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
How is DNA arranged in a Bacteria cell?
Large circular DNA, No histone proteins, several plasmids, and not bound by a nucleus just rather sits in the cytoplasm
56
Non sex chromosomes
Autosomal
57
What happens in Prophase?
- 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
What happens in Metaphase?
-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
What happens in Anaphase?
-Spindle fibers contract and shorten, pulling a set of chromosomes to opposite poles of the cell -The sister chromatids separate at the centromere
60
What happens in Telephase?
-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
What happens in Cytokinesis?
-The cytoplasm begins to cleave forming the cleavage forrow -the cytoplasm is divides forming two genetically identical cells
62
What is the relationship between linkage, and distance separating loci of genes
The closer the loci of genes, the more the genes are likely to be linked
63
What is the term for chromosomes from you mother, and those from your father?
Mother = Maternal Father = Paternal
64
How do stem cells undergo differentiation?
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
What is IPS
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
How is gene expression done?
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
Explain LAC Operon?
- 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
What can speed up the rate of transcription?
- cAMP-CAP binds to the RNA polymerase
69
What is the difference between continuous and discontinuous variation?
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
What is methylation and how does it work?
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
What is acetylation and how does it work?
A variation due to envoirnmental changes, which results in loose packing of DNA so transcriptional factors can bind and genes are expressed
72
How are epigenetic changes passed on?
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
What is the name of the flattened sacs of the Golgi apparatus
Cisternae
74
What is the name of the flattened sacs of the Golgi apparatus
Cisternae
75
Define Polygentic
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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