A5 - Human Genetics Flashcards
What is an allele
A gene that gives different traits
What is a trait?
A genetically determined characteristic
What is a dominant allele?
An allele that produces a certain phenotype in an organism always represented by a CAPITAL letter
What is a recessive allele?
An allele that will not affect an individual. This is represent by a LOWER case letter and needs 2 copies of the same lower case letter to represent a trait
What does homozygous mean?
The same alleles
What does heterozygous mean?
Two different alleles
What does genotype mean?
The genetic information of a person
What does phenotype mean?
This is the resulting appearance of an individual from the genetic makeup
How many copies of a dominant allele is needed for a characteristic to be expressed?
1
How many copies of a recessive allele is needed for a characteristic to be expressed?
2
What are the 3 recessive conditions you need to know?
- cystic fibrosis
- PKU
- sickle cell
What is the only dominant condition you need to know?
Huntington Disease
To get all marks in your exam for punnet square questions what MUST you include?
- Draw the punnet square correctly
- What would the probability be for the individual
- Is it a dominant or recessive condition?
- What are the parents alleles? (Homozygous or Heterozygous)
- Is the condition recessive or dominant?
- What is the overall genotype of the affected individual?
What do each square of the punnet square represent?
25%
What does 2 squares of the punnet square represent?
50%
What does 3 squares of the punnet square represent?
75%
Can you be a carrier of Huntington’s disease?
No
What is/causes Down’s syndrome?
A condition where a baby is born with an extra chromosome. A baby is at higher risk of getting this if their mother is over the age of 35
What are the symptoms/affected PIES of Down’s syndrome?
- flat nose (physical)
- struggle to speak and learn (social)
- anxiety (emotional)
- stubbornness (intellectual)
How is Down’s syndrome treated?
- speech and language therapist can help speaking
- physiotherapist can help walking if they have low muscle tone
What is Huntington’s disease?
A brain disease that is inherited
What causes Huntington’s disease?
- A mutation in the gene for a protein called huntingtin
- Inheritance
What are the symptoms/affected PIES of Down’s syndrome?
- slurred speech (physical)
- concentration and memory decline (intellectual)
- lack of emotions (emotional)
- social isolation (social)
Can Huntington’s disease be cured?
No
What is/causes PKU?
A change in gene that helps create an enzyme needed to break down phenylalanine
What are the symptoms/affected PIES of PKU
- frequent tantrums (emotional)
- self-harm (physical)
- social withdrawal (social)
- brain damage (intellectual)
What are the treatments for PKU?
- a lifetime diet of foods without phenylalanine
- PKU formula to get enough protein without phenylalanine
What is sickle cell disease?
A group of haemoglobin related blood disorders
How is this caused?
Inheritance
What are the symptoms/affected PIES of sickle cell?
- painful episodes (physical/emotional)
- yellowing of skin, eyes and mouth (physical)
- cognitive impairment (intellectual)
- feelings of anxiety, shame, isolation (social)
What are the treatments for sickle cell?
- pain medicine
- blood transfusion
- vaccines
- bone marrow transplant
What is cystic fibrosis?
An inherited condition that causes sticky mucus build up in the lungs and digestive system
What causes cystic fibrosis?
A mutation in the gene and this is an inherited condition
What are the symptoms/affected PIES of cystic fibrosis?
- poor growth (physical)
- no intellectual effects
- risk of developing clinical depression (emotional)
- barriers forming friendships, lack of independence (social)
- can’t socialise with people also with cystic fibrosis
What are the treatments for cystic fibrosis?
- no cure
- antibiotics to prevent and treat chest infections which makes mucus easier to cough up
What is the amniocentesis diagnostic method?
A small amount of amniotic fluid which is the water around the uterus is tested using a thin needle which takes the baby’s cells which contains genetic information. This is performed on woman who are 15-18 weeks pregnant.
Why do woman have the amniocentesis procedure?
There are foetal cells that can be tested for genetic disorders like Downs Syndrome
What are the risks of the amniocentesis procedure?
- miscarriage
- infection in the uterus
- leaking amniotic fluids
What happens if a woman is tested positive during the amniocentesis procedure?
If tested positive for a disorder and the termination of the pregnancy is chosen, this will be at a later stage of pregnancy and is likely to be more distressing.
What is the Chronic Villus Sampling?
When a small sample of tissue is taken from the placenta for testing. The sample will contain some of your baby’s cells which contains genetic information. This is usually done from 11-14 weeks of pregnancy.
Why do woman have the Chronic Villus Sampling procedure?
Because these results can tell you if the genetic condition has been discovered.
Are there any risks of the Chronic Villus Sampling procedure?
- miscarriage
- infection
What is the difference between Amniocentesis and Chronic Villus Sampling?
Amniocentesis uses a small amount of amniotic fluids from the sac surrounding the foetus whereas, CVS test a small cell from the mothers placent. Amniocentesis is also done from 15-18 weeks whereas, CVS is done earlier from 11-14 weeks of pregnancy
For the Huntington Disease punnet square, what should the 1st punnet squares alleles be?
HH, Hh
For the Huntington Disease punnet square, what should the 2nd punnet squares alleles be?
Hh, hh
For the 3 main recessive conditions, what should their alleles be?
Both alleles need 1 UPPER case letter and 1 lower case letter
