Genetics

• This is a structure of chromosome

  A) chromatid

  B) centromere

  C) telomers

  
• Euchromatin is the type of chromatin that is lightly packed, gene rich and active in transcription
• Heterochromatin is the type of chromatin that is tightly coiled, has repetitive patterns
• Constitute heterochromatin is tightly packed, always coiled and may assist in gene regulation
• Methylation Mutes transcription
• Acetylation Activates transcription
• Epigenetic deals with factors "around" gene, influencing gene expression but not gene itself and this can also be passed down to offsprings
• Humans have 23 homologous pairs of chromosomes
• Humans have 22 autosomal chromosomes, with 1 being the largest out of all
• Humans have 2 sex chromosomes
• Diploid means homologues
• Polyploidy means cell has more than 2 copies of homologous chromosome
• Common epigenetics methods include histone modification, mi & si RNAs and DNA methylation
• To calculate the number of haploid chromosomes (which is basically a pair of 2 diploids X X), we need to divide the number of diploid chromosomes by 2
• Meiosis occurs only in eukaryotes
• Human cells undergoing meiosis are germline cells that produce sperm and ova
• The purpose of meiosis 1 is to separate homologous pairs
• Homologous pairs are similar but not identical chromosomes coming from 2 parents
• This ia stage of meiosis called prophase 1, and homologous pairs pair together and form a tetrade

  A) chiasmata

  B) homologous pairs

  
• The most unique thing that is happening during prophase 1 is cross-over
• This is a stage of meiosis called metaphase 1, where pairs line up randomly

  
• Genetic diversity during meiosis is brought by crossing over and independent assortment
• Haploid cell has 23 chromosomes
• Diploid cell has 46 chromosomes
• Polar body are those gametes produced by ovum that get degenerates so that only 1 ovum is produced after 2 rounds of meiosis
• After meiosis 1, haploid cells produced in humans are called secondary spermatocytes or oocytes
• The prupose of meiosis 2 is to separate sister chromatids
• Nondisjunction is when homologues pairs or sister chromatids do not separate during anaphase 1 or anaphase 2
• Aneuploid is a cell with an imbalance of chromosomes
• Monosomy is the loss of a single chromosome in the zygote (2n - 1) & it is usually nonviable
• Trisomy is the addition of a single chromosome in the zygote (2n + 1)
• Turner syndrome is monosomy of the sex chromosome (resulting in 45 chromosomes)
• Klinefelter's syndrome is a trisomy of the sex chromosomes (total of 47 chromosomes)
• In the end of replication, we have 46 chromosomes and 92 chromatids
• in the end of mitosis, we have 46 chromosomes
• In the end of meiosis 1, we have 23 chromosomes and 46 chromatids
• In the end of meiosis 2, we have 23 chromosomes
• Individual's genetic makeup is called genotype
• The expression of the trait is called phenotype
• Nucleotide sequence of a chromosome can be determined the earliest during prophase 1 of meiosis, because this is where cross over takes place