Genetics Flashcards
Genetic is the study of
inheritance
In a woman the sex chromosomes are XX, in the man they are
XY
Explain briefly what is meant by a gene?
section of DNA that carries the code for the production of a particular protein
Where in the nucleus would you find genes?
Chromosomes
What is the significance of the fact that the two allele pairs are located on different chromosome
they are Heterozygous
What is meant by non-coding DNA?
‘junk DNA’
Doesn’t form proteins
What is a chromosome?
structure found in the nucleus of a cell
What is meant by sex linked?
traits are controlled by the gene is on the X chromosome
What is meant by the term segregation as used in genetics?
Inherited characteristics are controlled by pair of factors these factors separate at gamete formation and only one factor is carried in each gamete
State the Law of independent assortment
at gamete formation either member of a pair of factors is equally likely to recombine with either member of another pair of factors
What is meant by DNA profiling?
unique pattern of DNA from one person that id compared with the DNA profile of another person
State 2 uses of DNA profiling?
- Crime
2. Medical
Explain what is meant by dominance
a gene which presents the recessive gene from working
Define Genotype
Genotype is the genetic make up of an organism
Define phenotype
Phenotype is physical make up of an organism
Define an allele
Different form of the same gene
Define Recessive
a gene that is prevented from working by a dominant gene
Define Homozygous
Both of the alleles are the same
A change in the genetic material of an organism is called
mutation
What is meant by genetic screening?
Testing a person’s DNA for the presence of abnormal or altered DNA
Define Nucleic acid
polynucleotide macromolecule
eg: DNA and RNA
What is non nucleic DNA
location: mitochondria
role: organelles reproduce without the nucleus
Define Heredity
The passing of features from parents to offspring by means of genes
Define species
group of similar organisms capable of inter-breeding to produce fertile offspring
What is non-coding DNA?
DNA that doesn’t code for a protein is also known as ‘Junk DNA’
Define a codon?
three bases in sequence it assembles an amino acid during protein synthesis
What is Gene expression?
Way in which the genetic code in a gene is decoded and used to make a protein
What is a gene
collection of codons, it contains the genetic code to form a protein and controls particular characteristics
What is meant by genetic screening?
Test to establish the presence or absence of a gene or altered gene
Give a brief outline of genetic screening
- Radioactive section of DNA is added to a DNA sample with a gene of the person being tested
- DNA probe only attaches to a normal gene
- If the DNA probe doesn’t attach the gene is altered
Name the scientists that described the structure of DNA
Watson and Crick
What does DNA stand for
Deoxyribonucleic acid
What is the shape of the DNA
Double helix
What does nucleotide consist of
1) phosphate group
2) deoxyribose sugar
3) base
What are the four different bases that exist?
1) Adenine
2) Guanine
3) Thymine
4) Cytosine
Which bonds are between complementary base pairs?
Hydrogen bonds
How many Hydrogen bonds are present between
- adenine and thymine
- guanine and cytosine?
- 2 hydrogen bonds
2. 3 hydrogen bonds
How can DNA be stable
an enormous number of hydrogen bonds
What are bases adenine and guanine classified as
Purines
What are bases thymine and cytosine called
Pyrimidines
In DNA, nitrogenous bases occur in complementary pairs. Explain the term complementary as used here
Each base has a corresponding matching base
What is the function of DNA
- Heredity material (passes genetic info from parents to offspring in the form of genes)
- Human chromosomes are composed of DNA and Protein
- Syllabus statement (each chromosome carries a series of genes in linear order along its length)
Briefly describe the nature of the genetic code
- codon is 3 bases in a sequence
- each codon codes for one amino acid
- gene consists of a collection of codons who code for one protein
- the codon sequence determines the amino acid sequence in a protein
- mRNA copies the genetic code from DNA and brings it to the ribosome in the cytoplasm where protein synthesis occurs
Define DNA replication
DNA makes exact copies of itself
List 2 stages of DNA replication
- Opening of the DNA double-helix
2. The synthesis of complementary nucleic acid strands alongside the existing strands to form 2 identical helices
Give an account for DNA replication
- occurs in interphase (part of cell division which involves making an exact copy of DNA)
- Hydrogen bonds break down
- Two strands separate
- DNA acts as a strand to form a new complementary strand
- DNA Nucleotides from the cytoplasm move to the nucleus and match up with their corresponding nucleotide on the exposed DNA strands
- 2 exact copies of DNA are made called helices
- Each new double-strand rewinds to form a double helix
- Each DNA molecule is half new and half old and identical
- This process requires energy from ATP and Anabolic enzyme DNA polymerase is a catalyst for assembly of DNA nucleotides
What does RNA stand for?
Ribonucleic Acid
What are the similarities in DNA and RNA
- Both have nucleic acids
2. Both contain bases adenine, guanine and cytosine
How does DNA differ from RNA?
1. DNA- double-strand
sugar
Base=thymine
Location=nucleus
2. RNA- single strand
ribose
Base=Uracil
Location=Nucleus and cytoplasmName the 3 types of RNA and give a brief account for each
- Ribosomal RNA (rRNA)
- forms ribosomes
- holds mRNA in place during protein synthesis
- Messenger RNA (mRNA)
- transcribes the genetic code from DNA
- carries the code to the ribosome
- Transfer RNA (tRNA)
- transfers amino acids to mRNA
- tRNA attaches to its complementary mRNA placing its amino acid in the correct sequence within its own protein
- each amino acid has its own tRNA
- anticodon is complementary to mRNA codon
Each mRNA codon specifies one of three possible outcomes during protein synthesis. Name these three possible outcomes
- Start codon
- Codon which assembles an amino acid
- Stop codon
How are 2 strands of DNA joined together?
Hydrogen Bonds
What us junk DNA
non-coding DNA
What was the first procedure that you followed when isolating DNA from plant tissue?
- Chop onion into pieces
What was the reason for that procedure?
To disrupt the structure and allow cytoplasm to leak out
Washing up liquid is used in the isolation. Give a reason for its use
It breaks down membranes
Salt is also used in the isolation. explain why
to clump the DNA
What is a protease?
An enzyme that breaks down protein
Why is a protease necessary when isolating DNA
DNA combines with protein in a chromosome
The final stage of the isolation involves the use of frozen-cold ethanol
- Describe how it used
- For what purpose is it used?
- Add slowly down the side of the test tube
2. To bring DNA out of the solution
What plant did you use when isolating DNA
Onion
It is usual to chop the tissue and place it in a blender. Suggest a reason for this
Chopping- releases the cytoplasm
Blending- Breaks down the cell walls
For how long should the blender be allowed to run?
3 seconds
Washing up liquid is normally used in this experiment. What is its function
It breaks down the membrane
Salt is also used in this experiment to suggest why
to clump the DNA
The final separation of the DNA involves the use of alcohol. Under what condition is the alcohol used?
Ice-cold
Which base can link only to Thymine?
Adenine
Which base can link only to Cytosine?
Guanine
