Genetics
IB Biology Genetics
IB Biology Genetics
Kartei Details
| Karten | 50 |
|---|---|
| Sprache | English |
| Kategorie | Biologie |
| Stufe | Andere |
| Erstellt / Aktualisiert | 11.03.2013 / 18.05.2018 |
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What are the effects of down syndrome?
Hearing loss
Visual disorders
mental and growth retardation
What is done to prevent down syndrome?
It is being tested for in expectant mothers
How is down syndrome tested for?
A maternal bood test records HCG (Human Chorionic Gonadotropin) and AFP (Alpha-fetoprotein) levels, chemicals released during pregnancy
A lower level of AFP and doubled level of HCG indicates a high chance of down syndrome
Further tests would then be carried out
How can chromosome abnormalities be confirmed?
Through a karyotype; an organised image of chromosomes at metaphase
Where can samples for a karyotype be taken from?
The amniotic fluid or placenta
What is the genotype?
The alleles of an organism
What is the phenotype?
The characteristics of an organism
What is a dominant allele?
An allele that has the same effect on the phenotype no matter if it is hetero- or homozygous
What is a recessive allele?
An allele that only has effect if it is present in homozygous state
What is a codominant allele?
Pairs of alleles that both affect the phenotype when in a heterozygote
What is the locus?
The specific region on the chromosome where the gene is found
Define homozygous
Having two identical alleles of a gene
Define heterozygous
Having two different alleles of a gene
What is a carrier?
A heterozygous individual bearing an unexpressed defective gene
What is a test cross?
Testing a suspected heterozygote by crossing it with a known homozygous recessive
What are eukaryote chromosomes made of?
DNA and Proteins
What are the chromosome facts?
1. The number of chromosomes per species is fixed
2. The shape of a chromosome is characteristic
3. The chromosomes of a cell occur in homologous pairs
4. Chromosomes hold the hereditary factors - genes
5. Chromosomes copy themselves
What is a gene?
A heritable factor that controls a specific characteristic
What is an allele?
One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene
What is a genome?
The whole of the genetic information of an organism
What is a homologous chromosome?
Chromosomes that occur in diploid cells, comtaining the same sequence of genes, but have come from different parents
What is a sister chromatid?
During interphase the DNA is replicated so a chromosome will have two identical sister chromatids when it enters cell division
How do mutations occur, and how can the chance of occurrence be increased?
Mutations occur randomly, but the chance of occurrance can be increased by mutagens e.g. radiation, uv light and poisons
What do mutations affect?
Transcription and translation
List two common mutation examples
Substitution of bases
Base insertion and deletion causing frameshifts
What is the most common genetic disease and what does it do?
Sickle-cell anemia causes the haemoglobin molecules to stick together when in tissues of low oxygen concentration, which can lead to the blocking of capillaries
What type of process is meiosis?
Reduction division
In meiosis, what is the nucleus at the beginning and at the end?
Diploid nucleus (2n) --> haploid nucleus (n)
How many divisions does meiosis consist of?
What happenes to the parent cell during meiosis?
The one diploid parent cell divides into four genetically distinct haploid daughter cells
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