Component 2: Continuity of Life Flashcards
1
Q
Give the Function of the following plant components:
1) Petal
2) Stigma
3) Stamen
4) Sepal
A
1) Releases Nectar to attract pollinators
2) Sticky so pollen will land on it
3) Transports sucrose, water and mineral ions to the pollen grains
4) Protects the developing flower
2
Q
Give 4 Comparisons of Wind and Insect pollinated flowers
A
Wind: - Petals usually absent or unscented - Large quantities of small pollen grains - Large external feathery stigma - External Anther Insect: - Colourful, scented petals and nectar - Smaller quantities of sticky pollen - Internal, smaller stigma - Internal anther
3
Q
What are the genetic consequences of self-pollination?
A
Self fertilisation therefore less genetic variation
4
Q
How are plants adapted to reduce the likelihood of self-pollination?
A
- Male and Female parts mature at different rates
- Stigma and Stamen exist at different levels/heights
- Seperate male and female flowers/plants
- Genetic incompatibility (cannot pollinate itself)
5
Q
Describe the Development of the male gamete in plants
A
1 meiotic division of a microspore to form 4 haploid microspores, followed by 1 mitotic division to produce a pollen grain consisting of 2 haploid nuclei
6
Q
What is the tapetum?
A
A layer of cells around the pollen sac providing nutrients and regulatory molecules
7
Q
What is dehiscence?
A
The opening of the Anther to allow pollen to leave
8
Q
How does a pollen grain prevent drying out whole being transferred between flowers?
A
The tapetum prevents desication
9
Q
What is inside a pollen grain?
A
The generative nucleus and tube nucleus
10
Q
Describe the development of the female gamete in plants
A
A meiotic division of a megaspore to produce 4 megaspores whereby 3 degenerate. 1 of the megaspores undergoes 3 mitotic divisions to produce 8 haploid nuclei within the embryo sac
11
Q
What is the collective name for the female part of the plant and what does it consist of?
A
Carpel- Style, Stigma and Ovary
12
Q
What does the ovule consist of in plants?
A
An embryo sac containing 7 nuclei
13
Q
What are the names of the nuclei within the embryo sac?
A
2 Polar nuclei
2 x synergids
Ovum
(3 x antipodal cells)
14
Q
Explain the process of double fertilisation
A
Pollen grain lands on the stigma, producing a pollen tube. The pollen tube grows down the style by secreting hydrolytic enzymes. The pollen tube grows between the integuments and through the micropyle to the embryo sac. 2 male nuclei enter the embryo sac, one fuses with the ovum to form a zygote. The other fuses with the polar nuclei to form a triploid endosperm.
15
Q
What is Pollination?
A
The transfer of pollen grains from the anther to the stigma
16
Q
What is fertilisation?
A
The fusion of a Male and Female gamete to produce a zygote
17
Q
What similarities are there between fertilisation in humans and plants?
A
Male gamete is delivered to the female gamete.
Use of hydrolytic enzymes.
18
Q
What do the following structures befome after fertilisation has occured?
1) Zygote
2) Triploid Endosperm
3) Integuments
4) Ovule
5) Ovary
A
1) Embryo
2) Endosperm tissue
3) Testa/Seed Coat
4) Seed
5) Fruit
19
Q
Define Germination
A
The development of a seed into a functioning plant
20
Q
Why must food reserves be mobilised in plants and how is this done?
A
Food reserves are insoluble in water. Water is taken up causing the tissues to swell and mobilise the enzymes.
21
Q
Describe the process of germination in plants
A
The seed coat ruptures as the radicle pushes its way through first. The radicle grows downwards and the plumule upwards. The cotyledons remain underground. The pumule is bent over like a hook to protect from soil erosion, as it unfurls it begins to make food through photosynthesis.
22
Q
What are the 3 main requirements for germination and why are they needed?
A
- Water, mobilises enzymes
- O2, used in aerobic respiration
- Suitable temperature, regulates enzyme activity
23
Q
Explain how gibberellic acid is used in the process of germination
A
Gibberellic acid, a growth regulator, is produced and diffused inro the aleurone layer. It switches on genes in the aleurone layer resulting in transcription and translation. Protease hydrolyses proteins to amino acids which are used to make amylase. Amylase diffuses out of the aleurone layer and hydrolyses starch to maltose and glucose. Sugars diffuse back into the embryo for use in respiration.
24
Q
What is the function of the scrotum?
A
Keeps the temperature of the testes at a lower temperature than the rest of the body
25
What is the function of the testes?
Produces testosterone and sperm
26
What is the function of the epididymus?
Stores sperm and transports it from the testes
27
What is the function of the Vans Deferens?
Transports mature sperm to the urethra
28
What is the function of the seminal vesicle?
Produces a mucus secretion which aids sperm mobility
29
What is the function of the prostate gland?
Produces an alkaline secretion that neutralises the acidity of urine and aids sperm mobility
30
What is the function of the Urethra?
Transports urine and semen from the body
31
What is the function of the penis?
Contains the external opening for urination and to deliver semen
32
What is the function of the human ovary?
Production of eggs and reproductive hormones
33
What is the function of the oviduct?
Transports egg from ovaries to uterus. Site of fertilisation of the egg
34
What is the function of the Uterus?
- Muscular walls
| Main function is to hold foetus until maturity
35
What is the Endometrium?
The mucus membrane lining the uterus- is shed during menstruation
36
What is the function of the vagina?
- Sexual activity
- Childbirth
- Menstruation
37
What is the function of the female urethra?
Acts as a passageway for urine
38
Describe the proccess of spermatogenesis
Occurs in the seminiferous tubules. The diploid spermatagonia divide by mitosis to produce primary spermatocytes. After the 1st meiotic division haploid secondary spermatocytes. These divide again by meiosis they form spermatids which differentiate into spermatozoa.
39
What is the function of Sertoli Cells?
They secrete a fluid which nourishes the sperm and protects them from the immune system of the male.
40
Describe the process of Oogenesis
Occurs in the ovaries. Oogonia are formed before birth, they undergo mitosis to form primary oocytes. They begin mitosis but pause at prophase 1. At puberty, hormones stimulate the follicles to develop. Each month several follicles start to develop but only 1 becomes a graafian follicle. The primary oocyte completes the 1st meiotic division to form the haploid secondary oocyte and a polar body. The mature graafian follicle bursts to release the secondary oocyte which begins meiosis but is paused at metaphase. Upon fertilisation the division is completed to form an ovum and 2nd polar body. The ovum and sperm nuclei fuse to form a zygote.
41
After ovulation what does the graafian follicle become?
The corpus luteum which produces hormones during pregnancy
42
How do the primary follicles form?
The germinal epithelium divides to form follicle cells which surround the primary oocytes.
43
How does the spermatozoa travel from the vagina to the oviduct?
The oocyte produces chemoattractants. Sperm swim through the cervix and uterus to the oviduct.
44
What surrounds the secondary oocyte?
- Corona Radiata
| - Zona Pellucida
45
Describe the process of capacitation
Sperm can only fertilise and ovum once capacitation has taken place. This is the removal of cholesterol and glycoproteins from the cell membrane of the acrosome; making the sperm more permeable to calcium ions
46
What is the function of the acrosome?
Releases proteases which digest the cells of the corona radiata. Upon contact with the Zona Pellucida the acrosome ruptures and releases another protease which hydrolyses the Zona Pellucida
47
What is the acrosome reaction?
The acrosome enzymes digest the corona radiata and zona pellucida to allow the sperm and oocyte membrane to fuse.
48
What is the cortical reaction?
The prevention of entry of additional sperm, the Zona Pellucida is chemically modified to make it less permeable to sperm.
49
Explain the process of ‘cleavage’
After fertilisation, the zygote begins to divide repeatedly by mitosis. Producing a hollow ball of cells called the blastocyst
50
Explain the process of ‘Implantation’
The development of the zygote continues during its passage down the fallopian tube. After 6 days the blastocyst reaches the uterus and embeds in the endometrium.
51
What are the cells around the blastocyst called?
Trophoblast
52
What does the trophoblast develop into?
The Chorion
53
Why does the Chorion develop villi?
Increases the surface area for the ansorption of nutrients from the wall of the uterus.
54
Describe the main roles of the placenta
- Secretes hormones
- Exchange of nutrients, waste products and respiratory gases
- Protects foetal capillaries from mothers high blood pressure
- Protection from the mothers immune response
55
Explain the role of the chorionic villi
Acquire blood capillaries which are connected to the umbilical vein. They increase surface area for diffusion
56
Explain the role of the intervillous spaces
Contain the mothers blood and surround the chorionic villi creating a shorter diffusion pathway
57
How do maternal and foetal blood supplies maintain a concentration gradient?
Counter-current flow
58
Which 4 hormones are involved in the menstrual cycle?
FSH
Oestrogen
LSH
Progesterone
59
What is the function of the FSH hormone?
- Stimulates growth of the graafian follicle
| - Stimulates release of Oestrogen
60
What is the function of the LH hormone?
- Stimulates ovulation
| - Conversion of the graafian follicle into corpus luteum
61
What is the function of Oestrogen?
- Rebuilds endometrium
- Stimulates release of LH
- Inhibits release of FSH
- Secondary sexual characteristics
- Inhibits prolactin and oxytocin
62
What is the function of Progesterone?
- Maintains endometrium
| - Inhibits release of FSH and LH
63
The developing embryo releases HCG, what is its function?
Maintains the corpus luteum
64
How is progesterone used during childbirth?
A decrease on progesterone levels allows the uterine wall to contract
65
What is the function of oxytocin?
Stimulates contraction of the uterine wall
66
What is the function of Prolactin?
Stimulates glandular tissue in the mammary glands to synthesise milk.
67
Define ‘Genotype’
The genetic composition of an organism
68
Define ‘Phenotype’
The visible characteristics of an organism as a result of genotype/environment
69
What is a Gene?
A length of DNA on a chromosomec coding for a particular polypeptide
70
What is Monohybrid Inheritance?
The inheritance of a single characteristic, concerning 2 or more alleles of one gene
e.g height, colour
71
What will the phenotype ratio be when 2 heterozygous organisms breed?
(Monohybrid Inheritance)
3 Dominant : 1 Recessive
72
What is Co-Dominance?
When both alleles of a gene contribute to the phenotype - the alleles are equally dominant
73
Define ‘Dihybrid Inheritance’
The inherits of 2 genes, coding for 2 contrasting characteristics
74
What is Linkage?
When both alleles for a characteristic are passed on by the same parent due to crossing over of alleles
75
How do sex chromosomes result in sex linked conditions?
- Males only need 1 form of a recessive allele to show characteristics (only has to be present on the X chromosome)
76
What is a mutation?
A change in the amount, arrangement or structure in the DNA of an organism
77
Give 3 reasons why mutations rarely show in the phenotype
1) Degenerate base: 3rd codon doesn’t have an effect
2) The mutation may exist on an intron, a non coding region
3) Many mutations are recessive
78
Name 2 types of mutagens and how can mutations be described?
1) Ionising radiation
2) Mutagenic chemicals
a) Spontaneous: happen without an apparent cause
b) Random: appear to happen at an equal probability anywhere in the genome
79
How can mutagenic chemicals cause mutations?
They can slide between base pairs preventing the replication of the correct nucleotide
80
What is a carcinogen?
Anything that increases the risk of cancer by causing mutations
81
Describe 4 ways in which mutations can happen
1) Gene point: single base change
2) Chromosome mutation: damage and insufficient repair to chromosomes
3) Aneuploidy: Whole chromosome may be lost or added
4) Polyploidy: Extra whole sets of chromosomes if the cell fails to divide
82
Name the different types of gene point mutation
- Deletion
- Substitution
- Insertion
83
How can polyploidy be beneficial to an organism?
More chromosomes = More likely to have advantageous characteristics
e.g. disease resistance
84
Why are triploids usually sterile?
Unable to form homologous pairs at meiosis
85
Why are mutations in somatic cells not passed on to offspring?
The mutation doesnt exist in the gametes so the genetic code for the mutation can not be inherited
86
When do mutations cause cancer?
If the proto-oncogene or tumour suppressor gene has a mutation, division may occur uncontrollably, causing cancer
87
Give 2 reasons why most mutations in somatic cells do not effect an organism
1) Tumour suppressor genes prevent cells dividing too quickly
2) The bodies immune ststem will attack mutated cells
88
What is the difference between benign and malignant tumours?
Benign: Only present in one area of the body
Malignant: Spread around the body, invading tissue forming multiple tumours
89
What are a proto-oncogenes and how do they become oncogenes?
A proto-oncogene codes for a protein that contributes to cell division.
If the proto-oncogene develops a mutation that can cause cancer it becomes an oncogene
90
What is beneficial mutation?
If it provides the organism with an advantage for survival
91
What is DNA methylation and what is its effect?
When a methyl group is added to cytosine.
| The more heavily methylated a region of DNA is, the less likely it will be transcribed.
92
What happens in histone modification?
Changes to histone proteins alters their interaction with DNA, reducing transcription.
93
What are 2 possible consequences of epigenetic changes?
1) genomic imprinting: if genes are inactive in gametes, the inactivity may be passed on
2) X inactivation: The switching off of an entire chromosome
94
What is the male gamete in plants?
The male nuclei within the pollen grains.
| NOT the pollen grains themselves
95
How does variation occur?
the combination of genetic and environmental factors as well as epigenetics
96
Name and explain 2 types of competition
Intra-Specific : between individuals of the same species
| Inter-Specific : between individuals of different species
97
What is a species?
A group of similar organisms that are able to interbreed to produce fertile offspring
98
What is the assumption when using that hardy-weinberg equation?
- A large randomly mating population in the absence of mutation and migration
99
what does p, p2, q, q2 and 2pq represent?
```
p = dominant allele
p2 = dominant genotype
q = recessive allele
q2 = recessive genotype
2pq = Heterozygous genotype
```
100
What is genetic drift?
When variation in gene frequencies occur by chance.
| e.g. a few members get isolated and start a new population
101
What is the founder effect?
A few individuals from a population start a new population with a different allele frequency
102
Name 5 mechanisms that can lead to reproductive isolation
- Behavioural isolation e.g different mating call
- Mechanical isolation e.g un-complementary genitalia
- Gametic isolation (prevention of fusing)
- Hybrid inviability (prevents development of embryo)
- Hybrid sterility (infertile offspring produced)
103
What is Polyploidy?
When more than 2 sets of chromosomes are present
104
What is the difference between allopatric and sympatric speciation?
Allopatric : new species formed in different geographical locations
Sympatric : new species formed in the same geographical location
105
What was the aim of the human genome project?
To produce a complete map of the human genome, identifying single genes and what they cause
106
Give 2 findings from the human genome project
1- Humans have less genes than expected
| 2- Less than 7% of proteins were specific to vertebrates, showing closer evolutionary relationships
107
What was the 100k genome project?
Sequenced 100,000 genes from NHS patients to identify causes of diseases and highlight potential treatments
108
Which organisms have had their DNA sequenced?
Bacteria, worms, fruit fly’s, yeast and humans
109
Why would conservationists be interested in DNA sequencing?
Shows evolutionary relationships and indicates which species may need protection
110
What is PCR?
a semi conservative replication of DNA in a test tube.
111
In PCR how is the DNA prepared and what are the 3 steps of PCR?
DNA is dissolved in a buffer and mixed with DNA polymerase, nucleotides and short pieces of DNA called primers
1: Separating the double strand (95°c)
2: Annealing the primers (55°c)
3: Synthesising new DNA (70°c)
112
Give 3 uses of PCR
- Phylogenetic studies
- Paternity cases
- Forensic Science
113
Briefly explain the 6 steps of gel electrophoresis
1: DNA is extracted
2: Fragments are separated by length
3: Nylon Membrane used to pick up the fragments
4: Luminescent DNA probes attach to the fragments
5: A film is placed on top and left overnight
6: Film is exposed showing the pattern of the genetic fingerprint
114
Name 4 enzymes used to obtain fragments of DNA and their functions
Restriction endonuclease: cuts DNA at recognition sites
Reverse Transcriptase: produces DNA from mRNA
DNA ligase: Joins the sugar phosphate backbone
DNA polymerase: joins nucleotides during transcription
115
Give 6 steps to obtain fragments of DNA
1: location of the gene
2: Isolation of the gene
3: Insertion if the gene into a vector
4: Transfer of DNA into a host cell
5: Identification of cells that have taken up the gene
6: Cloning of host cells
116
Give 4 uses of genetic screening
- Carrier screening
- Pre implantation diagnosis with IVF
- Newborn baby screening
- Presymptomatic tests eg Huntingtons
117
Name 2 different types of Gene therapy and how they differ
Somatic cell therapy or germ line therapy
| Changes to somatic cells cannot be passed down however changes in germ line could be inherited
118
What is genomics?
The study of the structure, function, evolution and mapping of genomes
119
How can genomics improve healthcare?
* more accurate diagnosis
* predict the effect of drugs
* new and improved treatments
120
What is the goal of tissue engineering?
To repair, improve and replace biological functions
121
What are stem cells?
An undifferentiated cell capable of dividing by mitosis to become different types of specialised cells
122
Name 2 types of stem cells and where they are obtained from
Embryonic stem cells (3-5 days after fertilisation)
| Adult stem cells (From bone marrow or muscle tissue)
123
What is a deme?
Sub-group within a population that may breed more often with eachother than the rest of the population
124
What is speciation?
the development of separate species due to demes becoming isolated
125
What is the difference between allopatric and sympatric speciation?
Allopatric - isolated in different locations
| Sympatric - in the same geographical location
126
What is stabilising selection?
The average phenotype may provide greater advantage therefore extremes become less common over time.
127
What is Directional selection?
As an environment changes, one extreme may provide an advantage therefore the average phenotype shifts in the direction of the extreme.
128
What is disruptive selection?
The average phenotype becomes less advantageous so both extremes become more favourable/common.
129
What is geographical isolation?
When the population becomes split due to a physical barrier such as mountains or a river.
130
What is behavioural isolation?
Where mating rituals or courtship displays change or become unrecognisable forming separate mating groups which will eventually become different species.
131
what is morphological isolation?
The exoskeleton of insects is rigid so genitalia must be complementary, if not new species can form over time.
132
What is gametic isolation?
Barriers may prevent the fusion of gametes eg membranes only being permeable to their own species
133
What is seasonal isolation?
Reproductive organs mature at different times throughout the year so only certain organisms can reproduce at any one time
