Transcript File - singhscience

B1 Smart Teach
Foundation
Session 3
Keywords
Key word
Definition
Nucleus
Place inside a cell that contains the DNA (chromosomes).
DNA
A molecule found in the nucleus of cells, it’s job is to give
instruction to make proteins.
Gene
A section of DNA that codes for one protein.
Allele
Different version of a gene (example: blue eye allele and
brown eye allele).
Chromosome
X shaped structure made of DNA (found in the nucleus).
Genetic Disorder
A physical problem caused by a different allele.
Carrier
Someone who carries the allele for a genetic disorder
without having the disorder.
Recessive allele
A recessive allele only shows if the individual has two
copies of the recessive allele.
Dominant allele
A dominant allele always shows, even if the individual only
has one copy of the allele.
Genotype
Describes the genetic make-up of an organism (the
combination of alleles).
Phenotype
describes the observable, physical characteristics that an
organism has.
Genetic Disorders
Two genetic disorders you need to know about:
Cystic Fibrosis – Over production of mucus
Sickle Cell Disease – Abnormally shaped red
blood cells.
Exam Question
The diagram shows the genetic inheritance of cystic fibrosis (CF) in a family.
Cystic fibrosis is a genetic disorder caused by the CF recessive allele.
1.
2.
What is an allele?
Complete the punnet square
to show how cystic fibrosis is
inherited if both parents are
carriers.
3.
Give the percentage chance of a child being
a carrier of CF when both parents are carriers
of CF.
50%
Punnet Squares
• Make sure you put the mothers alleles in the side
labelled mother and the fathers alleles in the side
labelled father.
• Dominant allele first.
• A carrier will always
have one dominant
allele and one
recessive allele.
• If it asks for percentage
chance, you must write
the percentage.
Percentage chance =
Probability =
Symptoms of Cystic Fibrosis
• An overproduction of thick sticky mucus which
can lead to:
-
Weight loss
Infertility
Breathing problems
Tiredness
Problems with digestion
Exam Questions
1. Describe how cystic fibrosis can cause problems
with the absorption of food and oxygen in a
person with this disorder (3 marks).
2. Explain why a person can be underweight due
to cystic fibrosis (2 marks).
Answers
1. Describe how cystic fibrosis can cause
problems with the absorption of food and
oxygen in a person with this disorder.
Answers
2. Explain why a person can be underweight due
to cystic fibrosis (2 marks).
Sickle Cell Disease
Sickle Cell Disease can cause a change in the
shape of a red blood cell.
Eye colour inheritance
Eye colour often comes up on the exam.
• The diagram below shows the inheritance of eye colour in a family.
• The allele for brown eyes is (B) and the allele for blue eyes is (b).
1.
2.
3.
What is the genotype of Jacob?
What is the phenotype of Jenny?
Is Baby J male or female?
Eye Colour Punnet Square
BROWN eyes (B) – Dominant
blue eyes (b) – recessive
Exam Question
1.
Explain why two parents with the alleles BB and bb for eye colour are
unlikely to produce offspring with blue eyes.
You should draw a genetic diagram or Punnett square to help with your
explanation.
Easy marks!!
Unlikely but not impossible