B6: Genetics Flashcards
When is mitosis used?
In asexual reproduction
Mitosis [definition]:
Cell division that forms 2 daughter cells, each identical to the parent cell
Meiosis [definition]:
Cell division that forms 4 daughter cells, similar to the parent cell, with half the number of chromosomes than in the parent cell
When is Meiosis used?
In sexual reproduction
Gametes:
Sex cells
Fertilisation [definition]:
The process of reproduction where the nuclei of two gametes fuse to form a zygote
What are the 4 key stuctures of sexual reproduction?
- Cells divide by meiosis
- Male and female gametes fuse
- Offspring are non-identical
- Two parents
What are the gametes in animals?
Sperm and egg cells
What are the gametes involved in flowering plants?
Pollen and ovum cells contain the gammetes
Asexual reproduction [definition]:
The process of reproduction that forms genetically identical offspring from only one parent.
Key features of asexual reproduction [4]:
- Only one parent
- Offspring are clones
- Cells divide by mitosis
- Thre is no gamete fusion involved
What is the name of the cell formed by the fusion of two gametes?
Zygote
Asexual reproduction is common in….
single-celled organisms
Reproduction….[2]:
- Is neccessary to ensure the survival of a living species
- It is a life process and a characteristics of all living things
Why is it neccessary for organisms to asexually reproduce?
For growth and repair of damaged cells
What is the name of the process of when bacteria divivdes?
Binary fission
Diploid cell [definition]:
A cell that has a full 2 sets of chromosomes (46 chromosomes)
Haploid cell [definition]:
A cell that has only 1 set of chromosomes (23 chromosomes)
As soon as the embryo reaches a threshold size…
cells begin to differentiate
Stages of Meiosis [4]:
- The 2 pairs of chromosomes found in the parent diploid cell replicate
- The diploid cell then divides twice to give 4, genetically distinct, gametes (they are all haploid)
- During sexual reproduction,fertilisation occurs, restoring the normal number of chromosomes
- Once the gametes combine the new cells divide by mitosis, which increases the number of cells
Advantages of sexual reproduction [2]:
- Variation in offspring
- Artificial selection (selective breeding in plants and animals speeds up artififcial selection)
Which organisms can produce both sexually and asexually? [3]:
- Fungi
- Malaria parasites
- Strawberry plants
What are the 4 genetically different gametes produced during sexual reproduction called?
Haploid cells
Advantages of Asexual reproduction [3]:
- Asexual reproduction is faster
- Many identical offspring
- There is no second parent is recquired
Why is variation in offspring an advantage?
It increases the chances of a population being able to survive environmental change by natural selection
If an organism can reproduce sexually or asexually, it often…
reproduces asexually when conditions are good
Genome [definition]:
The genome is the entire genetic material of an organism
What are the levels of organisation in a genome?
[3]:
- DNA
- Genes
- Chromosomes
DNA [definition]:
A double helix polymer of nucleotides that contains genetic information and makes up genes
Gene [definition]:
A small section of DNA that codes for a sequence of amino acids, which combine to give a specific protein.
What does DNA stand for?
Deoxyribonucleic acid
Chromosome [definition]:
Long, coiled up strands of DNA that contain many genes
How many pairs of chromosomes are in a healthy human cell?
23
What is a Polymer?
A large molecule that is made of many repeating subunits
Organisation of genetic material in Eukaryotic cells [3]:
- The nucleus of eukaryotic cells contains chromosomes made of DNA molecules.
- Each chromosome contains a large number of genes.
- Each gene tells how a specific protein should be made.
Mutagen [definition]:
Anything that causes a mutation (A change in the DNA of a cell)
Types of Mutagens [4]:
- Exposure to radiation (radiation)
- Different chemicals
- UV rays
- Free radicals
When was the human genome project published?
2003
What was the purpose of the human genome project?
To successfully map out all the genetic information in the chromosomes of a human being
Potential effects of Genome sequencing [3]:
- The investigation of human evolutionary and migratory history
- Improving understanding of inherited diseases
- Identifying genes linked to different disorders
How could the completion of the Human Genome Project, and subsequent research on the human genome, be beneficial in tackling Cystic Fibrosis?
- The knowledge we have gained from the Human Genome Project and subsequent research can help us in identifying Cystic Fibrosis genes, allowing those carrying it to be made aware
- It could also further our understanding of the disorder and how we should be treating it.
Nucleotide [definition]:
Small units that repeat throughout the structure of the DNA
What holds the 2 strands of DNA together?
Attraction between opposite bases
What pairs with base T?
Base A
What pairs with base G?
Base C
What pairs with base A?
Base U
What pairs with base A?
Base U
What forms the long strands in DNA?
The sugar and phosphates
Protein Synthesis [definition]:
The process in which our body makes protein
Codon [definition]:
A sequence of three bases in DNA or RNA that codes for a single amino acid
What does the order of bases in amino acids tell us?
The order for combining amino acids to create particular proteins
What happens to a gene when a sequence of bases in the gene is altered?
The protein changes
The steps in proteinsynthesis [7]:
- DNA is unzipped so that the information is exposed
- MRNA nucleotides match up to their complimentary pair
- The MRNA detaches from the DNA and moves out of the nucleus into the cytoplasm
- The RNA joins to the ribosome in a cell
- A carrier molecule with a complimentary base brings the RNA with an amino acid
- Another carrier molecule arrives with another amino acid which attaches to the first one
- The amino acid chain continues until all the RNA has been matched up
What is a key feature of the structure/shape of a protein?
It is specific
What is a protein?
A chain of amino acids?
What happens to the amino chains directly after proteinsynthesis? [3]:
- The amino acid chain folds and formsbonds to determine its final structure
- These bonds are determined by the sequence of amino acids
- The final structure determines the function of the protein
If the order of bases on DNA changes, what happens to the proteins made using the DNA?
The amino acid sequence may change
Allele [definition]:
The name given to one gene in a pair
Genes exist in….
pairs
Heterozygous [definition]:
When an individual carries 2 different alleles for a gene
e.g Bb
Homozygous [definition]:
When an individual carries 2 copies of the same allele for a gene (e.g BB)
Mutation [definition]:
A permanent change in the nucleotide sequence of DNA
Mutation [definition]:
A permanent change in the nucleotide sequence of DNA
Mutations [2]:
- Mutations that happen continuously and normally only slightly affect proteins or don’t affect them at all
- Occasionally, a mutation may change the structure or shape of a protein
The outcome of mutations [3]:
- The outcome of a mutation is almost always detrimental to protein function.
- In enzymes, the substrate may no longer be able to bind to the active site.
- In structural proteins, their strength may be reduced.
survival advantages of mutations [2]:
- More rarely, a mutation may give a survival advantage, such as resistance to an antibiotic in bacteria.
- These mutations can be beneficial and represent the foundation of evolution by natural selection.
Mutation is…
Random
What is the function of non-coding DNA?
It is important for gene expression
What is a possible cause for mutation?
Genes being switched on and off
A dominant allele is…
always expressed, regardless of the identity of the other allele
How are dominant alleles represented?
With capital letters
When is a recessive allele expressed?
Only when the other allele is recessive
Recessive alleles are represented by…
lower case letters
What causes characterististics
[2]:
- In most cases, a characteristic results from multiple genes interacting
- However, sometimes, a single gene is responsible for a characteristic. such as red-green colour blindness
Genotype [definition]:
The combination of alleles an individual has for a particular gene (e.g BB, Bb or bb)
Phenotype [definition]:
The physical expression of the genotype/ an observed characteristic of the individual
What is an example of a phenotype?
Earlobes being attached or free. The alleles present will determine a characteristic unless the environment interferes.
Monohybrid inheritance [definition]:
Refers to the inheritance of traits determined by a single gene
What are Punnett squares?
They are diagrams that help us to visualise the outcome of a monohybrid cross
Punnett square structure [2]:
- The alleles of the parents are drawn along the top and side of a grid
- The pairs of alleles that the offspring could have are then filled into the grid
What type of allele causes cystic fibrosis?
A recessive allele
Cystic fibrosis [3]:
- It is an inherited disorder
- It s a disorder of cell membranes
- It causes thick, sticky mucus to build-up in the lungs and digestive system.
What is the genotype of a cystic fibrosis sufferer?
ff
Polydactyly [4]:
- Inherited disorder
- Polydactyly is a disorder where the sufferer has extra fingers or toes
- It is caused by a dominant allele
- It is suffered by heterozygotes
What type of allele causes polydactyly?
A dominant allele
If a sufferer of cystic fibrosis has non-suffering parents, what are the parents?
Heterozygotes
What can family trees be used to visualise?
The transmission of inherited disorders from one generation to the next
Different types of embryonic screening [3]:
- Pre-natal screening
- IVF with PGD
- Artificial insemination
Embryonic screening is a form of…
genome screening
Pre-natal screening is at…
foetal stage
IVF with PGD is at the…
embryonic stage
What does IVF stand for?
In Vitro Fertilisation
What does PGD stand for?
Pre-implantation genetic diagnosis
Advantages of Pre-natal screening [2]:
- Relatively accurate procedure
- May prevent the birth of children with severe disabilities
Disadvantages of Pre-natal screening [5]:
- Healthy embryos may be terminated
- Invasive/ painful procedure
- Risk of miscarriage
- Very expensive
- Goes against religion
Advantages of IVF with PGD [4]:
- The embryo can be screened before it goes into the mother
- Not invasive at all
- No risk of miscarriage due to screening
- Prevents the birth of a child with serious disabilities
Disadvantages of IVF with PGD [3]:
- Goes against religion
- All embryos that aren’t used are destroyed/ disposed of
- Expensive
Advantages of artificial insemination [3]:
- No risk of miscarriage due to screening
- Not invasive or painful procedure
- Prevents the possibility of recessive disorders
Disadvantages of artificial insemination [3]:
- Rise in demand of ‘designer babies’
- You only know about the father’s genes
- Mutations could happen at fertilisation
What is different about artificial insemination and the other screening procedures?
Artificial insemination is the screening of the sperm whilst the others screen the embryo or foetus
Why do we screen embryos?
To find out if there will be a specific disorder
What are the 2 types of pre-natal screening?
- Amniocentesis
- Chronic villus sampling
What is the difference between amniocentesis and chorionic villus sampling?
In CVS a small sample of the placenta, after birth, is taken for testing, whereas in amniocentesis a small amount of amniotic fluid (the water around the baby inside the uterus)
What is the advantage of not having any screening done?
Prevents any difficult decisions that may have to be made
What type of screening is embryonic screening?
Genome screening
What are the genes for a female?
XX
What are the genes for a male?
XY
What chromosome does a female egg have?
X
What chromosome does sperm have?
Either one X chromosome or one Y chromosome
How many chromosomes in a cell are responsible for sex determination and what are they called? [2]:
- One
- Sex chromosomes
What do we call the monomers that DNA strands are made of?
Nucleotides
What are nucleotides made up of? [3]:
- Pentose sugar
- Base
- A Phosphate
How many nitrogenous bases can be found in DNA?
4
What are the nitrogenous bases found in DNA?
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
How can a mutation in a gene result in a protein not carrying out its role correctly?
- The mutation may code for a different amino acid
- Different amino acids could alter the structure of a protein
- The altered structure means that the protein is the wrong shape to transport water
If a couple has multiple children, why can we not know for certain how many of their children would suffer from a disorder?
Punnett squares only work out the probabilities of having a certain phenotype
How many bases make up a codon when coding for an amino acid?
3
Sexual reproduction of malaria
still need to do this flashcard
What is base U?
Uracil
