2. Evolution Pt4 Flashcards
If your sex chromosomes are XX what gender are you?
Female
If your sex chromosomes are an X and a Y what gender are you?
Male
What are chances of having a boy or girl?
50%
Explain why probability of having a girl or a boy is 50%?
- the female egg will always produce an X chromosome
- but there’s a 50:50 chance of it being fertilised by a sperm with an X or Y chromosome
What did Gregor Mendel discover?
- 19th century monk
- he cross-bred different peas and recorded the characteristics of there offspring (yellow, green, smooth, wrinkly)
- he concluded that packets of information could be passed from parent to offspring in predictable patterns
Why did no one believe Gregor Mendel?
-at the time no one had seen a chromosome
And so didn’t understand his theory
-he didn’t publish his work so died before his work was recognised
Define genotype
Define phenotype
- The combination of allele inherited from the parents
- the visible characteristics this produces
Define dominate alleles
That you only need inherit one copy of that allele to be able to develop the characteristic
What the genotype of a mouse with a black phenotype?
If black is the dominate allele
BB
Bb
Define recessive alleles
You need to inherit two copies of the gene in order to develop the characteristic
What would be the genotype of a mouse with a brown phenotype?
Brown being recessive
bb
If both allele are the same the genotype is called…
Homozygous
If both allele are diffrent the genotype is called…
Heterozygous
What genetic diagram do you draw to work out the probability of inheriting a particular characteristic?
Punnett square
Some ………… May be influenced by a number of different ………..
Characteristics
genes
Define genetic disease
A diseases or disorder that can be passed on from parent to child
What is cystic fibrosis?
- A disorder of cell membrane (caused by a recessive allele)
- That cause various organs to become clogged with a thick, sticky mucus
Symptoms of cystic fibrosis?
- CF can damage the lungs, the pancreas and the reproductive system
- it causes repeated infections and can lead to death and infertility
What allele would you needed to get cystic fibrosis?
-it’s caused by a recessive allele, so you need to have two copies of the gene
What happens if you one dominate healthy allele and one with cystic fibrosis?
- you will have no symptoms but are a carrier
- 1 is 25 people in the UK are a carrier approx
What treatments are there for cystic fibrosis?
- Physiotherapy to help clear the lungs of mucus
- antibiotics to treat the infections
- enzymes to replace the ones missing from the pancreas and to try and thin the mucus
What is polydactyly?
When babies are born with extra digits (fingers or toes)
How is polydactyly inherited?
Caused by a dominate allele
Huntington is caused by a dominate allele. If a heterozygous mother has children with a healthy Homozygous father, what are the chances of their third child developing Huntington?
50%
What is one future treatment that could cure a genetic recessive disease?
- it could be possible to insert a healthy copy of the gene into the necessary cells
- but for a dominate disease the unhealthy gene would have to be cut out of the DNA or silenced first
Right now the best way to inform a prospective parent if they carry the diseased ………. Before having children is …….. ……….
- gene
- genetic screening
What is embryo screening?
It can be used to test embryos for genetic diseases, either once a women is pregnant or part of the IVF process
What 2 treatments are available for pregnant women as they can’t do embryo screening?
Amniocentesis
Chronic villus sampling
Explain amniocentesis
- Collects amniotic fluid from around the foetus which will contain the baby’s cells
- they’re tested for the presence of diseased alleles
Explain chronic villus sampling
Removes cells from the developing placenta which can be tested for diseased Alleles
Advantages of screening
- reduces suffering as babies are born without the disease
- could eradicate a disease if everyone did it
- reduces financial cost on the parents/health service that treating the disease would involve
Disadvantages if embryo screening?
- is expensive
- can produce false positive so healthy foetuses are terminated
- collecting cells from a foetus can damage it or lead to a miscarriage
