SB3 - Genetics Flashcards
(89 cards)
1
Q
What is sexual reproduction?
A
Involves the joining of male and female gametes
2
Q
What gametes join together in sexual reproduction of flowering plants?
A
Pollen & egg cells
3
Q
How many chromosomes does a normal cell have?
A
46
4
Q
How many chromosomes does a gamete have?
A
23
5
Q
How is variation produced in sexual reproduction?
A
The genetic information from each parent is mixed
6
Q
What is asexual reproduction?
A
Involves one parent with no gametes joining
7
Q
What process does Asexual reproduction use?
A
Mitosis
8
Q
Why does asexual reproduction produce clones?
A
As there is no mixing of genetic information
9
Q
What are the advantages of Sexual reproduction?
A
- Produces variation in offspring
- Allows us to use selective breeding
10
Q
How is sexual reproduction allowing animals to produce variation in offspring an advantage?
A
- Means that if the environment changes it is likely that an organism in the species will have a survival advantage
- Variation decreases the chance of the whole species becoming extinct
11
Q
How is sexual reproduction allowing animals to use selective breeding an advantage?
A
- Organisms with different desirable characteristics can be bred to produce offspring
- Speeds up natural selection
12
Q
What are the disadvantages of Sexual reproduction?
A
- Time and energy are needed to find a mate
- It is not possible for an isolated individual
13
Q
What are the advantages of asexual reproduction?
A
- Only one parent is needed
- Uses less energy + is faster
- Favourable conditions - lots of identical offspring can be produced
14
Q
How does asexual reproduction use less energy?
A
As organisms don’t need to find a mate
15
Q
What are the disadvantages of asexual reproduction?
A
- It does not lead to variation in a population
- The species may only be suited to one habitat
- Disease may affect all the individuals in a population
16
Q
What is meiosis used to produce?
A
Haploid gametes
17
Q
What is meiosis?
A
Reduction division in a cell in which the chromosome number is halved from diploid to haploid
18
Q
What is DNA?
A
The material inside the nucleus of cells, carrying the genetic information of a living being
19
Q
What is DNA made up of?
A
Nucleotides
20
Q
What is a nucleotide made out of?
A
- Sugar
- Bases
- Phosphate group
21
Q
What is the double helix held together by?
A
Weak hydrogen bonds between complementary base pairs
22
Q
How are weak hydrogen bonds formed between bases?
A
Parts of DNA bases have slight electrical charges
A slightly negative charged part of one bases attracts a slightly positive part of another base = weak hydrogen bond
23
Q
How many hydrogen bonds does Cytosine & Guanine produce?
A
3 hydrogen bonds
24
Q
How many hydrogen bonds does Adenine & Thymine produce?
A
2
25
What does **Adenine** pair with?
Thymine
26
What does **Guanine** pair with?
Cytosine
27
What *shape* is **DNA**?
Double helix
28
What *important* information does **DNA** carry?
Genetic code - determines characteristics of a living organism
29
What *type* of **molecule** is **DNA**?
A polymer
30
What does the **order of different bases** form?
Genetic code
31
What is a **gene**?
A short section of DNA
32
What does each **gene** code for?
Many amino acids, which are joined together to make a specific protein
33
How many *types* of **amino acids** are there?
20
34
What is a **genome**?
All of the DNA in an organism
35
What are the *aims* of the **Human genome project**?
* To work out the order or sequence of all the three billion base pairs in the human genome
* To identify all the genes
* To develop faster methods for sequencing DNA
36
What has the **Human genome project** helped us *understand* the **human body**?
* Improved our understanding of the genes
linked to different types of disease
* Treatment of inherited disorders
* Tracing human migration patterns from the past
37
# Core practical: Extracting DNA
Describe the method you would use to **extract DNA** from a **fruit**?
1) Gently mix together some cold water, some salt and washing up liquid. Gently heat this mixture at a high temp for 5-10 minutes
2) Peel the skins of a fruit and chop into small pieces. Pulverise the fruit.
3) Add the solution from Step 1 to the fruit
4) Filter the solution using a few sheets of kitchen paper and a sieve. Pour the filtrate into a test tube
5) Add some pineapple juice to the filtrate and allow to rest for a few minutes
6) Add a few teaspoons of cold ethanol to the solution and wait a few minutes
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# Core practical: Extracting DNA
Why do we add **ethanol**?
Ethanol causes the DNA to precipitate out of the solution
39
# Core practical: Extracting DNA
What is the **expected observation** of this **practical**?
A white mass should precipitate at the top of the tube after 10 minutes (this is the DNA)
40
# Core practical: Extracting DNA
Why do we add a **protease enzyme solution / pineapple juice**?
This breaks down the proteins attached to the DNA - helps us to see it more clearly
41
How many **bases** code for an **amino acid**?
3
42
What *determines* what type of **protein** is **produced**?
The different types and order of amino acids
--->Therefore it is the order of bases in DNA that determine which proteins are produced
43
What are the **steps** that make up **protein synthesis**?
* Transcription
* Translation
44
What is a **polypeptide chain**?
Amino acid sequences
45
What are some **uses** of **proteins**?
* Enzymes
* Hormones
* Structural proteins
46
How are **proteins** used as **hormones**?
They carry messages around the body
47
How are **proteins** used as **structural proteins**?
They provide structure and are physically strong
48
How are **proteins** used as **enzymes**?
They act as biological catalysts to speed up chemical reactions occurring in the body
49
What is **Transcription**?
DNA is transcribed and an mRNA molecule is produced
50
What is **Translation**?
mRNA is translated and an amino acid sequence is produced
51
Where does **Transcription** occur?
Nucleus
52
Describe & explain **transcription** in *protein synthesis*
* Part of a DNA molecule unwinds
---> exposes the gene to be transcribed
* RNA polymerase binds to a region of non-coding DNA just in front of the gene
* RNA polymerase then makes a complementary copy of the code from the gene
* mRNA molecule leaves the nucleus via a pore in the nuclear envelope
53
What does it mean for part of a 'DNA molecule to **unwind**' in **transcription**?
The hydrogen bonds between the complementary base pairs break
54
How does *'RNA polymerase make a complementary copy of the code from the gene'*?
By building a single-stranded nucleic acid molecule - mRNA
55
What is a **polynucleotide**?
Made up of many nucleotides linked together in a long chain
56
Give some *examples* of **polynucleotides**
* DNA
* RNA
57
What do **RNA nucleotides** contain instead of **thymine**?
Uracil (U)
58
Describe the **structure** of an **RNA polynucleotide**
* Alternating ribose sugars
* Phosphate groups linked together
* Nitrogenous bases of each nucleotide projecting out sideways
59
Where does **Translation** occur in **protein synthesis**?
Cytoplasm
60
Why must **DNA first be transcribed into mRNA** before it can be *translated into a protein*?
DNA cannot travel out of the nucleus to the ribosomes as it is too big to pass through the nuclear membrane
61
What is a **codon**?
Each triplet of bases on a mRNA molecule
62
Describe & explain **translation** in *protein synthesis*
* After leaving the nucleus, the mRNA molecule attaches to a ribosome
* tRNA molecules bind with their specific amino acids and bring them to the mRNA molecule on the ribosome
* The anticodon on each tRNA molecule pairs with a complementary codon on the mRNA molecule
* Peptide bond is then formed between the two amino acids
* Polypeptide chain is formed
63
What does the **ribosome** do after the **mRNA molecule** attaches onto it?
* The ribosome ‘reads’ the code on the mRNA in groups
* The ribosome translates the sequence of bases into a sequence of amino acids that make up a protein
64
Describe the **structure** of a **tRNA molecule**?
* Anticodon on one end
* A region where specific amino acid can attach at the other end
65
What is an **anticodon**?
A triplet of unpaired bases at one end
66
How many **tRNA molecules** can fit onto a **ribosome** at any one time?
2
67
What **molecules** are in the **cytoplasm** that is useful for **protein synthesis**?
* tRNA
* Amino acids specific to the tRNA
68
When does the process **translation** stop?
Until a ‘stop’ codon on the mRNA molecule is reached
69
What does **mRNA** stand for?
messenger RNA
70
What does **tRNA** stand for?
transfer RNA
71
What is a **genetic variant**?
Small changes in the order of bases that make up a strand of DNA
72
What is **genotype**?
Refers to the genes present in the DNA of an individual
73
What is **phenotype**?
Refers to the visible effects of those genes
74
What does **non-coding** mean?
The DNA bases do not code for the production of an amino acid
75
How does **genetic variants** in the **non-coding regions** of a **gene** affect the *phenotype*?
Influences the binding of RNA polymerase and altering the quantity of protein produced
76
Describe & explain how **genetic variants** in the **'non-coding' regions** of a **gene** affect the *phenotype*?
* If a mutation happens in the non-coding region to which RNA polymerase attaches
---> Can affect the ability of RNA polymerase to bind to it
* It can make it difficult for RNA polymerase to bind, less mRNA will be transcribed from the gene and less protein (that the gene codes for) will be produced
77
How does **genetic variants** in the **coding regions** of a **gene** affect the *phenotype*?
The gene may code for a different sequence of amino acids so it'll alter the activity of the protein produced
78
What are the *types* of **DNA mutations**?
* Insertions
* Substitutions
* Deletions
79
What is **substitutions**?
One of the bases is changed for another random bas
80
What is **insertions**?
An extra base is inserted into the sequence
81
What is **deletions**?
One of the bases is deleted from the sequence
82
What is the **issues** with **DNA mutations**?
| (insertion, deletions and substiutions)
It may change all the amino acids coded
83
What is an **allele**?
Different forms of a gene
84
What is a **dominant allele**?
Only one (out of the two alleles) is needed for it to be expressed and for the corresponding phenotype to be observed
85
What is a **recessive allele**?
Two copies are needed for it to be expressed and for the corresponding the phenotype to be observed
86
What is **homozygous**?
When both inherited alleles are the same
87
What is **heterozygous**?
When one of the inherited alleles is dominant and the other is recessive
88
What is a **chromosome**?
A structure found in the nucleus which is made up of a long strand of DNA
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