Biology > Topic 3 - Genetics > Flashcards

Topic 3 - Genetics Flashcards

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1
Q

What is sexual reproduction

A

Genetic information from two organisms ( a father and mother ) is combined to produce offspring genetically different to either parent
In sexual reproduction the parent produce gametes. In Animals this is sperm and egg cells

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2
Q

Gametes

A

The reproductive cells of a plant or animal. These are HAPLOID ( only 1 set of chromosomes )

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3
Q

Zygote

A

At fertilisation, the male gamete fuses with the female gamete to produce a ferilised egg called a ZYGOTE. This has the full set of chromosomes - DIPLOID

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4
Q

How does a zygote develop into an embryo?

A

It undergoes cell division by mitosis.
This embryo inherits characteristics from both parents, as it has recieved a mixture of chromosomes

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5
Q

How are gametes produced?

A

By meiosis

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6
Q

Meiosis vs mitosis

A

Mitosis produces clones. - Diploid
Meiosis doesnt produce identical cells - Haploid

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7
Q

Where does meiosis happen in the body?

A

In the reproductive organs

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8
Q

How does the FIRST DIVISION of meiosis

A
  1. before the cell divides, it duplicates its DNA
  2. The chromosoes line up in pairs at the centre of the cell - one of the pair from the organisms mum, one from their dad
  3. The pairs are then pulled apart, so each one only has 1 copy of each chromosome - some of the mum nad some of the dads chromosomes go into each cell

Each new cell with have a mixture of the mothers and the fathers chromos

Creates Genetic variation

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9
Q

How does the SECOND DIVISION of meiosis

A
  1. The chromosomes line up in the centre again, but ovbi not in pairs dun
  2. The chromatids of the chromosomes are pulled apart
  3. This creates 4 Haploid daughter cells - these are the Gametes

The gametes are all genetically different

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10
Q

What are the ADVANTAGES of ASEXUAL reproduction

A
  • can produce lots of offspring very quickly - This allows organisms to colonise a new area very quickly
    -One parent is needed - Organisms can produce whenever conditions are favourable, without having to wait for a mate
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11
Q

What are the DISADVANTAGES of ASEXUAL reproduction

A
  • there is no genetic variation in the population
  • ## Suceptable to environment changes, they cannot adapt
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12
Q

What are the ADVANTAGES of SEXUAL reproduction

A
  • Creates Genetic variation
  • Not suceptable to environment changes - adaptability
  • Natural selection and evolution makes these always better suited to their environment conditions
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13
Q

What are the DISADVANTAGES of SEXUAL reproduction

A
  • Takes more time and energy than Asexual reproduction, organisms produce less offspring in their life
  • Two parents are needed, a problem is an organism is isolated.
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14
Q

What is a DNA strand made of?

A

Dna is a polymer made up of Nucleotides

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15
Q

What does each nucleotide in a DNA consist of?

A

A sugar, a phosphate group and one base

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16
Q

What do the Sugar and phosphate group form in DNA?

A

The backbone to the DNA strand.
-> With the base added, they become a nucleotide

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17
Q

Where are the bases in DNA and what 4 bases are there?

A

The bases join to the sugars
Adenine - Thymine
Cytosine - Guanine

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18
Q

What is complementary base pairing?

A

The sugar bases will correspond and match up to another sugar base. They are held together by weak hydrogen bonds
A - T
C - G

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19
Q

How is DNA stored?

A

as chromosones

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20
Q

What are chromosomes

A

Long, coiled up peices of DNA found in Eukaryotic cells

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21
Q

What is a gene?

A

A section of DNA on a chromosome that codes for a particular protien with a specific sequence of bases

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22
Q

What is a genome?

A

all of an organisms DNA

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23
Q

How do you extract DNA from fruit cells?

A

Mash strawberries and put in a beaker containing a solution of detergent and salt
Detergent - Break down cell membranes to release DNA
Salt - Make the DNA stick together
Filter the mixture - get froth and big insolule bits out.
Gently add some ice cold alcohol to the filtered mixture
The DNA will start to come out of the solution as it is not soluble in ice cold alcohol. It will appear as a stringy white precipitate that can be fished out with a glass rod

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24
Q

What is the use of DNA?

A

DNA controlls the product of protiens in a cell ( protien synthesis)
DNA molecules contains a genetic code on which protien is built. The protien determines how the cells in the body work

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25
What is protien synthesis?
The production of protien
26
What are protiens made up of?
Amino acid chains folded in a specific way with each protien having its own specific number and order of amino acids. These amino acids are joined together by the order of the bases in the gene
27
Why do different protiens have different functions?
The amino acids fold up to give each protien a different, specific shape
28
How are amino acids coded for?
A base triplet
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What is a base triplet?
A sequence of 3 bases in a gene
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What is a triplet code?
A code based on base triplets
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What does a change in bases of a gene cause?
A genetic mutation. Some of these mutations can change an organisms phenotype
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How can a mutation occur?
Cell division or environmental factors
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How are mutations in non-coding DNA caused?
RNA polymerase attaches to DNA bases in the front of a gene. A mutation in this non- coding region may result in the RNA not binding well, reducing transcription.
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What are alleles?
different forms of the same gene
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Heterozygous
Both genes are different
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Homozygous
Alleles are the same
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Genetic variation
Caused by the different alleles inherited during sexual reproduction
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Environmental variation
affected by the surroundings
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Discontinuous variation
Where the data can only take a limited set of values
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Continuous Variation
the data can be any value in a range
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The human Genome project idea
- idea to find every single human gene
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The Human Genome Project 3 main applications
1. prediction and prevention of diseases 2. testing and treatment for inherited disorders 3. New and better medicines
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The Human Genome Project downsides
***Increases stress -*** If someone knows they have the gene succeptible to a certain disease, this could cause stress ***Gene-ism*** - people with certain flawed genes could feel under pressure to not re-produce ***Discrimination by employees or insurers*** - life insurance and hiring
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Where are protiens made?
In the cytoplasm by subcellular structures called ribosomes
44
Where is DNA found and where does protien synthesis happen?
In the cell nucleus and it can't move out of it because its too big. So the cell needs to get the information from the DNA to the ribosome in the cytoplasm
45
How is the information from DNA transported to the ribosome in the cytoplasm?
Transcription and translation (protien synthesis)
46
What is used in transcription (protien synthesis)
A Molecule called **messenger RNA (mRNA)** And RNA polymerase
47
What is mRNA
Messenger RNA. Like DNA, mRNA is a polymer of nucleotides but its shorter and only a single strand. It also uses **Uracil (U)** instead of **thymine (T)** as a base. | Uracil bonds to adenine
48
What is RNA polymerase?
the enzyme involved in joining together RNA nucleotides to make mRNA
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# PROTIEN SYNTHESIS Transcription
1) **RNA polymerase** binds to a region of **Non-coding DNA** in front of a gene 2) The **two DNA strands unzip** and the **RNA polymerase** moves along one of the strands of DNA 3) It uses the **coding DNA** in the gene as a template to make the mRNA. Base pairing between the *DNA and RNA* ensures that the *mRNA is complimentary to the gene* 4) Once made, the mRNA molecule *moves out of the nucleus* and joins with a ribosome
50
# PROTIEN SYNTHESIS Translation | Assembly
1) Amino acids are brought to the ribosome by another RNA molecule called **Transfer RNA (tRNA)** 2) The order in which the amino acids are brought to the ribosome *matches the order of base triplets* in **mRNA (codons)** 3) Part of the **tRNA's structure** is called an **anticodon** - its complimentary to the codon for the amino acid. The pairing of the codon and the anti-codon makes sure that the amino acids are brought to the ribosome in the correct order. 4) The amino acids are joined together by the ribosome. This makes a **polypeptide (protien)**
51
What are the base triplets in mRNA called?
Codons
52
How does Non-coding DNA affect the binding of RNA polymerase?
Before transcription can happen, mRNA has to bind to a region of non-coding DNA in front of a gene. If a mutation happens in this region of DNA, then it could affect the ability of RNA polymerase to bind to it - easier/difficult - This affects how much mRNA is transcribed and therefore how much of the protien is produced. And, depending on the function of the protein, the phenotype of the organism may be affected by how much of it is made.
53
what are alleles?
different versions of a gene we have 2 alleles for each gene in our body (one in each chromosome, in chromosome pairs)
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Homozygous
2 alleles for a gene that are the same
55
Heterozygous
2 alleles for a particular gene that are different
56
How is dominance/recessiveness shown in allele diagrams
Capital letter for dominant Lowercase letter for recessive e.g if a person has one dominant allele and one recessive allele it would be shown as "Cc"
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How are dominant/recessive alleles shown?
Dominant - CC or Cc Recessive - cc
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Genotype
combination of the genes you have
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Phenotype
The (shown) characteristics you have
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What can genetic diagrams show?
the Inheritance of a single characteristic
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what is the inheritance of a single characteristic called?
monohybrid inheritance
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What can be used to show how dominant and recessive traits are inherited in a single characteristic? | Monohyrbrid inheritance
A monohybrid cross Punnet squares
63
How would you show the monohybrid inheritance from heterozygous and homozygous (dominant) parents
Parents genotypes: X x (het) X (Homo) I XX Xx X I XX. Xx
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What does the 23rd chromozome code for?
Sex Male characteristics- XY Female characteristics- XX | eggs have X and sperm has X or Y so sex depends on the sperm
65
what is a family pedigree?
A family tree of genetic disorders
66
How is a characteristic sex-linked?
when the allele that codes for it is located on the sex chromozome (X or Y)
67
Why are most genes on the sex chromosomes are only carried on the X chromosome?
The Y chromosome is smaller than the X chromosome and carries fewer genes. So most genes of the sex chromosomes are only carried on the X chromosome
68
Why are men more likely than women to show recessive characteristics for genes that are sex-linked?
As men only have one X chromosome they often only have one allele for sex-linked genes Because men only have one allele, the characteristic of this allele is shown even if it is recessive. This makes men more likely than women to show recessive characteristics for genes that are sex-linked
69
What are sex-linked genetic disorders?
disorders caused by faulty alleles located on the sex chromosomes
70
How are alleles shown on sex-linked genetic diagrams?
Both the chromosome and allele are written in the genetic diagram - e.g if the gene is on the X chromosome: XⁿXⁿ, XᴺXⁿ, XᴺY, Xⁿ Y
71
What are the 4 potential blood types in humans and the alleles that cause it?
O, A, B, AB Iᴼ, Iᴬ, Iᴮ A and B are codominant O is recessive
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