Genetics Flashcards
Variation
There are differences between numbers of the same species i.e. a population
Species
A group of organisms capable of interbreeding and producing fertile offspring.
What must be for a new species to form?
For a new species to form , all offspring must be fertile
Genetics
The study of heredity
Heredity
The passing on of features from parents to offspring by means of genes (also called genetic inheritance)
What is the unit of inheritance?
Gene
Where is a gene found?
On a chromosome
What does a chromosome contain?
a number of genes
What do genes contain?
Instructions to make a particular protein
What does a gene influence?
It directly influences the characteristics of an organism
What are controlled by genes?
Characteristics are controlled by genes.
What is an example of how characteristics are controlled by genes?
e.g. everyone has genes which determine hair colour
What is an example of genes creating different characteristics?
There is more than one type of gene for hair colour that you could have
Are all genes expressed?
Not all genes are expressed
What do genes produce? Give an example.
Genes produces characteristics or traits that are inherited e.g. gene for tallness
What influences characteristics?
Characteristics = heredity + environment
What are chromosomes made up of?
Chromosomes are made up of 60% protein and 40% DNA.
What are genes arranged along?
Genes are arranged along the DNA of the chromosome
Describe the structure of chromosomes, what they contain, how they occur and where they are found.
Chromosomes are thread like structures that contain DNA and Genetic information. They occur in pairs and are found in the nucleus of all cells
What are chromosomes?
Chromosomes are long pieces of DNA, with supporting proteins.
What are genes?
A gene is a short length of DNA that codes for a specific protein and therefore genes hold the information needed to build and maintain the body
Do genes locations change?
Genes have fixed locations: each gene is in a particular place on a particular chromosome.
What chromosomes do diploids contain?
Diploids have 2 copies of each chromosome, one from each parent. This means 2 copies of each gene.
How many chromosomes do we have?
We have 46 chromosomes, or 23 pairs.
What are 44 of the 46 chromosomes called? How are they labeled and what are their sizes?
44 of the 46 chromosomes are called autosomes and are numbered 1 through 22. Chromosome 1 is the longest, 22 is the shortest.
What are the other two chromosomes (not autosomes) called?
The other 2 chromosomes are the sex chromosomes: the X chromosome and the Y chromosome.
What sex chromosomes do males and females have?
Males have an X and a Y, females have 2 X’s: XY vs. XX.
What is the basic rule of sex determination?
If a Y is present the person is male
What happens to the X and Y chromosomes in males for meiosis?
The X and Y chromosomes separate and go into different sperm cells
How many sperm carry the X and Y chromosomes?
1/2 the sperm carry the X and the other half carry the Y.
What do all eggs have with regard to chromosomes?
All eggs have one of the mother’s X chromosomes.
What does the Y chromosome have on it?
The Y chromosome has the main sex-determining gene on it, called SRY.
What happens with regard to sex about 4 weeks after fertilization?
About 4 weeks after fertilization, an embryo that contains the SRY gene develops testes, the primary male sex organ.
If an embryo develops testes, what do they secrete?
The testes secrete the hormone testosterone.
What does testosterone do after it has been secreted by the testes of the embryo?
Testosterone signals the other cells of the embryo to develop in the male pattern.
What are the causes of inherited variations?
- Sexual reproduction
- The independent assortment of chromosomes when gametes are formed
- Crossing over during Meiosis - this allows genes to move between chromosomes
- Mutations
Are offspring identical to their parents?
Offspring are similar to their parents but are not identical
What are differences between parents and offspring caused by?
This is caused by crossing over
Can humans survive with 1 or 3 copies of any chromosome except for X and Y?
Except for the X and Y, humans don’t survive with only 1 copy of any chromosome. Also, 3 copies is lethal in most cases.
What is Down-Syndrome and what is another name for it?
Down-Syndrome is the most common human aneuploidy. It is also called trisomy-21, meaning 3 copies of chromosome number 21.
What can chromosomes be broken by?
By X-rays and by certain chemicals.
What happens usually when chromosomes are broken?
The broken ends spontaneously rejoin, but if there are multiple breaks, the ends join at random.
If there are multiple breaks and the ends join at random, what does this lead to?
This leads to alterations in chromosome structure.
Are the syndromes with alterations in chromosome structure as well defined as with number variations? Explain.
There are lots of ways chromosomes can change structure, so the syndromes are not as well defined as with number variations.
What are point mutations?
These are changes in just one base pair of a gene.
What happens if a point mutation occurs in a gamete or in a cell that gives rise to gametes? Give an example.
If a point mutation occurs in a gamete or in a cell that gives rise to gametes, it may be transmitted to offspring and to a succession of future generations e.g. sickle cell anaemia.
How does a point mutation causing sickle cell anaemia affect a person?
Damage is caused to the red blood cell membrane, resulting in a cellular lifespan of only a few days. Due to the sickle cell shape, small capillaries may become blocked.
What are other causes of mutations?
Radiation, Sunlight (containing UV radiation), smoking
What does DNA stand for?
Deoxyribonucleic acid
What is DNA?
Hereditary material that carries and passes on genetic information. It is a nucleic acid made up of nucleotides.
What is the structure of DNA?
DNA is a double helix. It consists of two parallel strands each with a series of bases to the inside. The bases are directly opposite each other and they link each other in pairs. These links form the steps of the ladder.
What do the bases A, T, C and G stand for?
Adenine, Thymine, Cytosine, Guanine
What is the base pair rule?
Adenine can only join to Thymine and Guanine can only join to Cytosine.
What percent of DNA is composed of genes? What is the rest of DNA made up of?
Only about 3% of DNA is composed of genes. 97% of DNA is non coding DNA or junk DNA.
What are coding DNA and what are coding DNA in genes called?
The parts of DNA that contain information to make RNA or protein. Coding DNA in genes are called exons.
What are non coding DNA and what are non coding DNA in genes called?
The parts of DNA that do not contain critical information for the production of protein. They are now thought to play a role in gene expression. Non coding DNA within genes is called introns.
What are the differences between DNA and RNA?
DNA: Double strand, Sugar is deoxyribose, has Thymine, Very long, Self replicating, Found only in the nucleus.
RNA: Single strand, Sugar is ribose, Has Uracil, Short molecule, Not self replicating, Found in nucleus and cytoplam.