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Genetics . http://www.youtube.com/watch?v=CBezq1fFUEA&list=PL3EED4C1D684D3ADF. 4.1.1. State that eukaryote chromosomes are made of DNA and proteins. 4.1.2. Define gene , allele and genome . Gene- heritable factor that codes for a certain trait Ex: eye color
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Genetics http://www.youtube.com/watch?v=CBezq1fFUEA&list=PL3EED4C1D684D3ADF
4.1.1 State that eukaryote chromosomes are made of DNA and proteins.
4.1.2 Define gene, allele and genome.
Gene- heritable factor that codes for a certain trait • Ex: eye color • Allele- what will be expressed in that gene • Ex: blue eyes • Genome- Collection of all of an organism’s genes • usually encoded in DNA • HGP
4.1.3 Define gene mutation.
Sequence change • Different amino acid possible • Can be beneficial • Mutagens
4.1.4 Explain the consequence of a base substitution mutation in relation to the processes of transcription and translation, using the example of sickle-cell anemia.
1/655 African Americans • Single base change • Change beta chain shape (needles)
4.2.1 State that meiosis is a reduction division of a diploid nucleus to form haploid nuclei.
4.2.2 Define homologous chromosomes.
Same • Length • Loci for genes • Shape
4.2.3 Outline the process of meiosis, including pairing of homologous chromosomes and crossing over, followed by two divisions, which results in four haploid cells.
http://www.youtube.com/watch?v=qCLmR9-YY7o&list=EC3EED4C1D684D3ADFhttp://www.youtube.com/watch?v=qCLmR9-YY7o&list=EC3EED4C1D684D3ADF
Interphase • Chromosomes not condensed • DNA replicates- S1
Prophase I • Nuclear membrane breakdown • DNA condensing • Spindle fibers • Centrioles move • Move towards equatorial plate • Longest phase of meiosis
Metaphase I • Line up in center • Chromosomes most condensed • Crossing over (Metaphase and Prophase)- chiasma • Independent assortment
Anaphase I • Homologous pair movement • “Arrow shape” of pairs
Telophase I • Sets at opposite sides • Nuclear membrane may reform (species) • Cleavage furrow • End meiosis I
Prophase II • Nuclear membrane breaks down • Spindle fibers reform
Metaphase II • Line up center • Independent assortment
Anaphase II • Spindle fibers contract • One chromatid per pole
Telophase II • Nuclear membranes form • Haploid • Crossing over variation
4.2.4 Explain that non-disjunction can lead to changes in chromosome number, illustrated by reference to Down syndrome (trisomy 21).
Can happen in Meiosis I or II • Result in too few or too many of one chromosome • Monosomy-more deadly, trisomy
4.2.5 State that, in karyotyping, chromosomes are arranged in pairs according to their size and structure.
Pictures during metaphase • 23 pairs
4.2.6 State that karyotyping is performed using cells collected by chorionic villus sampling or amniocentesis, for pre-natal diagnosis of chromosome abnormalities.
Obtain fetal cells to do a karyotype to find out if baby has disorder like Downs • Amniocentesis- removal of amniotic fluid containing fetal cells • Centrifuge separates chromosomes into size • Chorionic villus sampling- samples chorion • Must be after 8 weeks of pregnancy • Uses catheter
4.2.7 Analyse a human karyotype to determine gender and whether non-disjunction has occurred.
4.3.1 Define genotype, phenotype, dominant allele, recessive allele, codominant alleles, locus, homozygous, heterozygous, carrier and test cross.
4.3.2 Determine the genotypes and phenotypes of the offspring of a monohybrid cross using a Punnett grid.
2:2 ratio • Heterozygous crosses 3:1 • Each fertilization independent of others • Larger the population, the closer to expected ratio
4.3.3 State that some genes have more than two alleles (multiple alleles).
Creates more phenotypes and genotypes • Example: Rabbit coat colour(C) has four alleles which have the dominance hierarchy: C > cch > ch> c • This produces 5 phenotypes, Dark(C_) , Chinchilla( cchcch), light grey (cchch,cchc), Point restricted (chch, chc) and albino (cc)
4.3.4 Describe ABO blood groups as an example of codominance and multiple alleles.
I is immunoglobulin • The Allele hierarchy is IA = IB > I • When A and B present, both expressed and both mask O
4.3.5 Explain how the sex chromosomes control gender by referring to the inheritance of X and Y chromosomes in humans.
23rd pair • X much longer than Y • X from mom Y from dad in boys • Theoretically 50/50 chance for gender, but some have predisposition • SRY gene (supposed to be found on tip of Y) determines gender
4.3.6 State that some genes are present on the X chromosome and absent from the shorter Y chromosome in humans.
4.3.7 Define sex linkage.
Genes on non-homologous region of X • Females spare tire other X, males don’t have this • More common in males • Boys inherit these from mom
4.3.8 Describe the inheritance of colour blindness and hemophilia as examples of sex linkage.
Genes on non-homologous part of X • Males always get affected gene from mother • Males cannot pass on affected gene to sons, but can to daughters