Biology - Core Flashcards
Huntington’s disease is a faulty allele on which chromosome?
4
What is Huntington’s disease?
A genetic disorder which affects the central nervous system.
What does HD cause?
Damage to nerve cells in certain areas of the brain.
Changes of Huntington’s Disease are…
Physical, mental and emotional - all are gradual.
Symptoms develop when…
Person reaches adulthood
Symptoms of HD include…
Tremors, clumsiness, memory loss, inability to concentrate,mood changes,
Who develops HD?
Everyone who inherits the allele.
HD is in which allele?
Dominant
Cystic Fibrosis is what in the UK?
The most common life threatening disease
CF affect what?
Cell membraines
Symptoms of CF include…
Thick mucus in the 1/ lungs 2/ gut 3/ pancreas
Difficulty breathing
Chest infections
Difficulty digesting food
Which allele is CF on?
Recessive
Will you always develop Cystic Fibrosis?
No, you can be a carrier
Is there a cure for CF.
No
The procedure for embryonic selection is called?
PGD - Pre-implantation Genetic Diagnosis
When does PGD take place?
After fertilisation, before implantation
How many cells do the embryos divide into for PGD?
8
How many cells are tested in PGD?
1
What is the cell tested for in PGD?
To see if it carries the allele for a specific disease
Risks of PGD
Faulse results, discarded healthy embargo’s, decreased chance in embryo survival
Which test is done between 14-16 weeks?
Amniocentesis
What is Amniocentesis?
Amniotic fluid is removed from the uterus through a needle, and is then tested for diease
Risks of Amniocentesis?
0.5% chance of miscarriage
small chance of infection
When is Chronic Villus Testing done?
8-10 weeks
What happens with CVT?
catheter in vagina - into placenta - chronic villa from placenta removed - tested for disease
Reliability of testing?
no test is 100% reliable and so genetic testing will always have a number of outcomes
Ethical considerations?
- should child be told if they carry the disease?
- family members may not agree or want to know the results
- if the test is positive - are you killing a child with an abortion/ forcing it to live unhappily
What is ASEXUAL reproduction?
reproduction not involving sex - cells divide
Which organisms reproduce asexually?
- all bacteria
- many plants
- some animals
What are the results of asexual reproduction?
two DAUGHTER cells are produced from the MOTHER cell - as they are the mother cell divided into two, they are exact genetic copies - clones
How do changes happen to clones?
From environmental factors - food, water etc.
What are runners?
shoots that will eventually break off and become new plants
What is artificial cloning?
removing the nucleus from an adult cell and transferring it into an empty, unfertillised egg cell
What is the importance of stem cells?
cloning depends on stem cells as they have the ability to become any cell type in the body
What are the two types of stem cell?
embryonic, adult
What are EMBRYONIC stem cells?
unspecialised, can develop into any cell (including more embryonic stem cells)
What are ADULT stem cells?
unspecialised, can develop into most but not all cells
What is a zygote?
the FIRST cell formed after the FERTILISATION of an EGG by a SPERM
What cells can be used to treat some illnesses or injuries?
stem cells
What happens once the zygote has divided 4 times (to reach 16 cells)?
the majority of cells in the embryo have become specialised
How do cells become specialised?
certain genes are switched on/ off
What follows cells becoming specialised?
the production of proteins specific only to that cell type
What can specialised cells divide into?
the same type of specialised cell
What are genes?
the basic unit for the instructions controlling how the cell develops functions, sections of DNA that describe how to make proteins
Where are genes found?
in long DNA strands called chromosomes
What is a chromosome?
a long strand of DNA molecules, each consisting of two strands forming a double helix
What is the main chromosome for human eye colour?
15
What is variation?
differences between individuals of the same species
What can variation be due to?
environmental or genetic factors (also a combination of both)
Define genotype
the genetic make up of an individual
Define phenotype
observable characteristics of an individual
What are alleles?
different versions of the same gene
What are dominant alleles?
the alleles that control the development of a characteristic, even if there is only one
What are recessive alleles?
the alleles that require both chromosomes to have control over development
Define homozygous
when two alleles are the same (DD, rr)
Define heterozygous
when two alleles are different (Dr, rD)
What are sex cells?
Eggs - ovaries
Sperm - testes
How many copies of each chromosome do sex cells carry?
1 (23 total instead of 46/23 pairs)
What determines the sex of an embryo?
a gene on the Y chromosome
What is the sex determining gene called?
SRY gene
What happens if the SRY gene is not present?
the embryo will develop into a female ( two X chromosomes)
What happens after 6 weeks?
gonads start producing ANDROGEN
What is androgen?
a male sex hormone - stimulates male reproductive organs to grow
What causes infertility?
even with the presence of the y chromosome, androgen may not be detected and so all sex organs are produced other than the uterus
Define Gonad
an organ that produces gametes; testes or ovaries
What are gametes?
ovaries or testes
