(P1) Topic 3: Genetics Flashcards
Asexual reproduction
One living organism, reproduction without sex
Sexual reproduction
Male and female, reproduction with sex
What kind of cells are gametes (sex cells)
Haploid cells
What are gametes formed by
Meiosis
What does sexual reproduction involve
The joining of male and female gametes- eggs and sperm
Why is sexual reproduction slower than asexual reproduction
A mate must be found
Where does asexual reproduction often occur
In bacteria and fungi
Do aphids do sexual or asexual reproduction
Asexual- they are born pregnant and as developed nymphs
What is parthenogenesis
Ability to reproduce asexually- a female can produce an embryo without fertilising an egg with sperm
What are body cells referred to as
Somatic cells
What are cells produced by meiosis referred to as
Gametic cells (gametes)
Are somatic cells diploid or haploid
Diploid
A gamete cells diploid or haploid
Haploid
What does diploid mean
Two sets of chromosomes, one from each parent
What does haploid mean
A single set of chromosomes
Steps of meiosis
Meiosis I and meiosis II
Prophase I
Metaphase I
Anaphase I
Telophase I
Prophase II
Metaphase II
Anaphase II
Telophase II
Why are all humans similar
We all have the same genes
What makes humans different
The inheritance of different alleles of genes
What do gametes form when they join together at fertilisation
A zygote
What amount of DNA do gametes have in them compared to normal body cells
Half
What is the average size of a chromosome- average amount of genes that it contains
Contains 1000 genes
What is a gene
A length of DNA that codes for a single protein
What is an allele
A version of a gene either dominant or recessive
What are the four bases in DNA
A- adenine
T- thymine
C- cytosine
G- guanine
What are the base pairs
A-T
C-G
What type of bonds are between bases
Hydrogen bonds
What is the order of bases known as
The genetic code
How many characteristics does each gene code for
One, as it contains its own unique base sequence
What forms a nucleotide
Deoxyribose, phosphate, and one of the bases
Which allele is functioning
Dominant
What is the recessive allele
Non-functioning
What is ribose
A sugar, like glucose, but with only five carbon atoms in its molecule
How is deoxyribose different to ribose
It has one less oxygen atom
How many copies of each chromosome do we get from each parent
One, so we get two copies of each gene
DNA extraction practical steps
1- turn kiwi into a pulp in a sealed bag
2- add soap + salt mixture (20ml)
3- filter the mixture into a test tube
4- place 2ml of ice-cold ethanol around the inside of the test tube
5- collect DNA salts on a stick- white stringy mass
Why is soap used in the DNA extraction practical
Detergent breaks down cell membranes (both cell membrane and nuclear membrane)- that’s how it kills bacteria
Why is salt used in the DNA extraction practical
Salt denatures lysosomes so we can extract DNA without the cell braking down
What do lysosomes do
Break down the cell when it thinks its dying
They are enzymes
Why use ethanol in the DNA extraction practical
To precipitate the DNA
Does ribonucleic acid have more or less oxygen than deoxyribonucleic acid
More
What does RNA stand for
Ribonucleic acid
How many strands does RNA have
One
How many strands have DNA have
Two
What sugars (bases) does RNA have
A- adenine
U- uracil
C- cytosine
G- guanine
Is RNA longer or shorter than DNA
Shorter, it has a shorter sequence of bases
What is RNA used for in cells
To make things- e.g make cells red
What are the three main types of RNA
mRNA- messenger RNA
tRNA- transfer RNA
rRNA- ribosomal RNA
What does mRNA do
Transfers DNA code to ribosomes for translation
Tells ribosomes to make proteins
Code to tell ribosomes what to do
“Master RNA”
What does tRNA do
Brings amino acids to ribosomes for protein synthesis
What are ribosomes made of
rRNA and protein
How are RNA molecules produced (transcription)
By copying part of the nucleotide sequence of DNA into complementary sequence of RNA
What does RNA polymerase bind to during transcription
Binds to DNA and separates the DNA strands
What does the RNA polymerase use the one strand of DNA as
A template from which nucleotides are assembled into a strand of mRNA
What region of the DNA does the RNA polymerase bind to to begin transcription
A promoter
What is another term for protein synthesis
Transcription
How many naturally occurring amino acids are there
20
What are the bonds in amino acids called
Peptides
What is another term for a protein
Poly-peptide
What is a codon
A sequence of 3 nucleotides that specifies a specific amino acid
What happens during translation
The cell uses information from mRNA to produce proteins
In what part of the cell does transcription occur
The nucleus
What part of the cell does mRNA move from and to
Cytoplasm to ribosomes
What does tRNA do to mRNA and what is obtained
The tRNA “reads” the mRNA and obtains the amino acids coded for
What do ribosomes do to amino acids and what is formed
They attach the amino acids and this forms a polypeptide chain (a protein)
What stops the polypeptide chain from continuing to grow
It reaches a stop codon
What do gene mutations result from
Changes in a single gene
What are causes of mutations
Environment
Random
Lifestyle
Drugs
Radiation (UV, X-Rays)
Chemicals (cigarette smoke, benzoyl peroxide, nitrate peroxide)
Infectious agents (HPV, helliobacter pylori)
What are the types of mutation that can occur
Substitution (change of a letter)
Reverse order
Deletion
Insertion
What is a mutation
A change to a gene caused by a mistake in copying the DNA base pairs during cell division, or by the effects of radiation or of certain chemicals
What is a phenotype
Characteristics that a certain set of alleles produce
What is a genotype
The alleles for certain characteristics that are found in an organism.
What is an allele
Different versions of the same gene
What is a gene + where is it found
A section of the long strand of DNA found in a chromosome, which often contains instructions for a protein
What is a genetic disorder
A problem caused by genes
Who was Gregor Mendel
A catholic priest, he was interested in inheritance, “Father of Modern Genetics”
What did Gregor Mendel invent
The idea of genetics
The words “allele”, “dominant”, “recessive”
What is Mendelian Inheritance
Simple inheritance- one gene = one characteristic
What are the genes that give a higher chance of breast cancer
BRCA1 and BRCA2
Why did few people listen to Gregor Mendel
Religion- he wasn’t a scientist, he was a monk
He didn’t speak English
Why was Gregor Mendels model of inheritance ignored
He had no evidence as DNA hadn’t been discovered yet so he couldn’t create a theory
What plants did Gregor Mendel use to test his model
Pea plants
What does cystic fibrosis cause the body to create
Thick, sticky mucus
Why is the mucus produced by cystic fibrosis dangerous
It clogs the lungs, leading to infection
It blocks the pancreas, which stops digestive enzymes from reaching the intestines where they are required to digest food
What is cystic fibrosis caused by
A defective gene
What chromosome is Haemophilia A linked to
X (X-linked)
Is the gene that causes haemophilia A recessive or dominant
Recessive
What does haemophilia A cause
Joint and muscle bleeds and easy bleeding
What does haemophilia A result from
Deficiency of procoagulant factor VIII
Why do males and females have different probabilities of inheriting the diseases from their parents
Males have one X chromosome, and and females have two
Why do sex-linked diseases not pass from fathers to sons
Sons only inherits the normal Y chromosome
Give two examples of sex-linked diseases
Red-green colourblindness
Haemophilia
What is the genotype for blood type A
AA or AO
What kind of blood can people with type A blood receive
A or O
What plasma antibodies does type A have
B
Is the allele for type A blood recessive or dominant
Dominant
What is the genotype for type B blood
BB or BO
What kind of blood can people with type B blood receive
B or O
What plasma antibodies does type B blood have
A
Is the allele for type B blood recessive or dominant
Dominant
What is the genotype for type AB blood
AB
What kind of blood can people with type AB blood receive
A, B, AB, or O
What plasma antibodies does type AB blood have
None
What is the genotype for type O blood
OO
What kind of blood can people with type O blood receive
O
What plasma antibodies does type O have
A and B
What is the positive/ negative gene called
The Rheus Gene
What happens if you receive the wrong blood
The blood clots and can cause death
What are antigens
Molecules located on the surface of cells that rigger a specific immune response
What are ways in which variation occurs
Sexual reproduction
Environment affecting the organism
How does sexual reproduction cause variation
Genetic information is exchanged between the male and female gametes
What of ways of measuring variation
Measuring height- shows continuous variation
Eye colour- shows discontinuous variation
Natural hair colour- shows discontinuous variation
What is continuous variation
Range of values with most in the middle
What is discontinued variation
Distinct groups
