DNA & Inheritance Flashcards
How many pairs of chromosomes does a human body cell have?
23
What is a gene?
A small section of DNA in a chromosome
What is DNA?
A double helix polymer
What do genes do?
They code for a specific sequence of amino acids in order to make a specific protein. It is the unit of heredity. They contain instructions for individual characteristics.
What is the genome?
The entire genetic material of an organism
What is DNA made of?
Two long strands of small units that repeat throughout the structure, called nucleotides
What does a nucleotide consist of?
Alternating sugar and phosphate sections and one of 4 types of bases attached to the sugar
What are the 4 bases called?
Adenine, Thiamine, Cytosine and Guanine
How does complimentary base pairing work?
A always joins with T
C always joins with G
Hydrogen bonds connect the bases (2 for C&G, 3 for A&T)
What holds the two strands of DNA together?
Attraction between bases
How does our body make proteins?
Protein synthesis
What is the ‘triplet code’
The sequence of 3 bases that code for an amino acid
How can we change the protein made by a gene?
By changing the sequence of bases in the gene
Describe the structure of DNA
A polymer consisting of nucleotides made up of phosphate, pentose sugar and a base attached to the sugar. The sugar and phosphate create the backbone (two strands), connected by attractions between complimentary nitrogenous bases, making a double helix shape
What are the steps in genetic profiling?
- Isolation - DNA taken e.g. by cheek swab and extracted from the cell’s nucleus
- Fragmentation - Chromosomes broken up into shorter segments of DNA by enzymes
- Separation - DNA fragments placed on gel and put through gel electrophoresis (electric current separating the fragments into size order)
- Comparison - Results can be compared to other DNA
What can genetic profiling be useful for?
Catching criminals (observing whether 2 DNA fingerprints are the same)
Identifying species
Paternity cases (identifying genes)
Identifying disease genes
What are the ethical issues associated with genetic profiling?
Invasion of privacy
Misuse of info
Set up crime scenes/mistaken suspects
Family problems
How do DNA fragments move in electrophoresis?
Big fragments move slowly and small fragments move further and faster
What are alleles?
Different forms/variants/versions of the same gene. Humans have pairs of every gene, so two alleles are present in one gene pair
What is the difference between the dominant and recessive allele?
A dominant allele is always expressed, regardless of the identity of the other allele while a recessive allele is only expressed if the other allele is also recessive.
What are identical alleles for the same characteristic called (e.g. AA or aa)
Homozygous
What are different alleles for the same characteristic called? (e.g. Aa)
Heterozygous
What is a phenotype?
An observed characteristic determined by the interaction between the genotype and the environment
What is a genotype?
The combination of alleles an organism has
Will a person with a heterozygous genotype receive the dominant or recessive phenotype?
Dominant
In a Punnett square, what names are given to the generations?
Parents - F0 generation
Offspring - F1 generation
Their offspring - F2 generation
etc.
Which Punnett square would give a 50:50 chance of each phenotype?
Rr*rr
Which combination of sex chromosomes (X&Y) produce offspring of male or female biological sex?
Female - XX
Male - XY
Which sex chromosome does an egg contain?
One X chromosome
Which sex chromosome does a sperm contain?
One X OR One Y chromosome
What does a Punnett square for gender determination look like?
The mother is always XX
The father is always XY
50% of the children are XX (girls) and 50% are XY (boys)
What is genetic engineering?
Changing the genetic material of an organism by removing, changing or inserting individual genes from another source to produce a desired characteristic
When is genetic engineering used?
Inserting genes into crop plants to give it resistance to herbicides
Inserting genes into crop plants to provide additional vitamins
Inserting human genes into bacteria to produce human insulin
Inserting genes into crop plants to give it resistance to insects
What are the advantages of genetically modified (GM) crops?
They generally show increased yields
They help provide nutrients missing in diets of people from developing nations (avoiding deficiencies)
Popular in some areas of the world and no complications so far
What are the advantages of genetic engineering?
Prevents inherited diseases
Improves food production efficiency
What are the disadvantages of genetically modified (GM) crops?
Could negatively impact wild flower and insect populations, reducing biodiversity
Could have long-term effects on human health after consumption
If transplanted genes managed to escape into the natural environment, we could accidentally create a ‘superweed’ that is resistant to herbicides
What are some concerns about genetic engineering?
Because it is recent, we do not know the long-term effects it may have
Some consider it unethical to create new life forms or move genes between species.
What is known as a permanent change in the nucleotide sequence of DNA?
A mutation
What is embryonic screening?
Testing an embryo for the presence of a particular allele or other genetic abnormality. It allows couples at risk of transmitting a genetic disease to ensure their future children are unaffected by the disease without going through the process of prenatal diagnosis
