Mutations Flashcards
What are mutations?
Any change in the genetic composition of an organism.
Why does a mutation occur
-could occur by chance
-could occur as a result of mutagens
What are mutagens
-physical or chemical agents that cause mutations.
When can gene mutations be transferred to children
Only mutations that occur in the sexual organs can be passed on
What are the 2 types of mutations
-Gene mutations
-chromosomal mutations
What are gene mutations?
-A change in the nucleotide sequence
When can gene mutations occur?
They can occur during:
- DNA replication
- Transcription of DNA and RNA
- Crossing over during prophase of meiosis
What are the four types of gene mutations?
-Substitution
-deletion
-insertion
-inversion
A change in the nucleotide sequence.
As a result…
As a result the code for protein synthesis changes and forms a faulty protein.
What happens in substitution?
-One nitrogenous base is replaced by another
-results in the alterations of one amino acid
-point mutation
What happens in deletion?
-one or more nitrogenous bases are lost
-results in a frame shift
- all base triplets are altered and consequently all the amino acids are
What happens during insertions?
-one or more nitrogenous bases are inserted
-all base triplets are altered and consequently also the amino acids.
-frame shift
How does a chromosomal mutation occur?
- it occurs when Meiosis doesn’t proceed properly which results in changes in one chromosome number or structure.
What is Aneuploidy?
- extra chromosomes or missing chromosomes in a cell.
Give examples of Aneuploidy.
- Down syndrome - 47 chromosomes.
- Turner Syndrome - only one sex chromosomes (XO)
- Klinefelter syndrome- extra sex chromosomes (XXY)
How does Down syndrome occur?
Occurs during the production of eggs during Meiosis when chromosomes number 21 doesn’t separate during Anophase 1
What is a zygote?
It is a fertilised egg cell that is formed when a female gamete and a male gamete join.
What is trisomy 21?
A genetic chromosome 21 disorder causing developmental and intellectual delays.
-Also known as Down syndrome.
What are the characteristics of Down syndrome? (9)
- small almond eyes
- ears situated lower down the head
- flat forehead
- short, stubby toes
- poor muscle tone
- flat nose bridge
- large tongue
- predisposed to heart disease
- mental retardation
What is the Maternal Age Effect?
- After the age of 35 the risk of complications like miscarriage, congenital disorders and high blood pressure.
What gender does the turner syndrome effect and what happens with the chromosomes?
- effects the development of females
- only one X chromosome (XO)
How many people develop turner syndrome?
1 out of 40 zygotes develop turner syndrome
What are the characteristics of turner syndrome? (7)
- abnormal growth - short in stature
- lack of female secondary sexual characteristics.
- sterile
- slight mental retardation
- webbed neck
- heart defects
- low hairline
What are Somatic Mutations.
They are mutations that occur in body cells and are not transmitted to the next generation. It can cause cells to become malignant.
Definition malignant.
- Cancerous
What gender does klinerfelter syndrome effect.
Males
- it causes men to have 2 or more X chromosomes ( XXY )
What are the characteristics of Klinefelter syndrome? (5)
- Abnormal development of the Tetris
- Infertile
- often tall
- produce a small amount of testosterone
- develop some female characteristics
What may reduce effects of klinefelter syndrome symptoms?
Testosterone treatment may reduce symptoms caused by Klinefelter syndrome.
What are Gametic Mutations?
- gametic mutations are mutations that occur in reproductive organs and they produce change in gametes. They are transmitted to the next generation.
Examples of reproductive organs. (4)
- ovaries
- testes
- anthers
- embryo sacs
Gametic Mutations may lead to…
Gametic mutations may lead to hereditary diseases.
What are the 3 different types of Gametic Mutations?
- lethal/harmful
- Beneficial
- neutral
How does a beneficial mutation occur?
If the mutation results in organisms adapting better to new or unfavourable conditions, they will survive and reproduce beneficial mutations.
What is Nature Selections?
- Nature “selects” the better adapted feature/ability and then this is passed to the next generation until all individual have it.
Where do small mutations occur?
Small mutations occur in the phenotype
What are some examples of beneficial mutations?
- Antibiotics resistant bacteria
- Peppered Moths in industrial Great Britain
What are Neutral Mutations.
Mutations that don’t affect the phenotype or they have no survival effect on the organism
What are some examples of Neutral Mutations?
- attached vs unattractive earlobes
- Heterochromia, a mutation that causes two different colored eyes
What is an example of Harmful Mutations?
- Albinism
-colour blindness.
Harmful mutations usually have
Usually autosomal recessive traits
What’s is Heterozygous and homozygous?
Heterozygous- having two different versions of a gene.
Homozygous- having two identical versions of the same gene
