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Milestone Minutes
Genetics
Week 3
Write notes in your Milestone Journal and answer the practice
questions.
Genetics
DNA and RNA are molecules essential for the transmission of
genetic information.
 DNA is a double stranded helix, contains the sugar deoxyribose, A-T & G-C
 RNA is single stranded, contains the sugar ribose, A-U & G-C, produces proteins
 DNA replication (copying)occurs prior to mitosis during the cell cycle
 Mitosis stages: prophase, metaphase, anaphase, telophase
 Mitosis results in two genetically identical daughter cells, occurs in autosomal cells,
diploid (asexual)
 Meiosis results in four genetically different gametes (egg & sperm), haploid (sexual)
 Recombination of genetic material (crossing over) occurs during anaphase 1 & 2 of
meiosis
Mendel was the father of genetics and put forth laws
concerning heredity.
 Law of Dominance -dominate alleles (capital letter) suppress recessive alleles
(lowercase letter)
 Law of Segregation -during fertilization gametes randomly pair to produce four
sets of alleles (monohyrid)
 TT=homozygous dominant, Tt=heterozygous, tt=homozygous recessive
 Genotype is the combination of alleles, Phenotype is the physical expression of
alleles
 Law of Independent Assortment -genes for traits are inherited independently of
each other (dihybrid)
 Segregation & Independent Assortment allow only one allele a gene to be
present in the gametes
Alterations (mutations) can occur during meiosis and change
the genetic code.
 Some environmental factors are mutagenic (sunlight, chemical waste, radiation, toxins)
 Insertion-addition of one or more nucleic bases in the genetic sequence, changes reading
frame
 Deletion-removal of one or more nucleic bases in the sequence, changes reading frame
 Substitution-switch of one or more nucleic bases in the genetic sequence, no change to
reading frame
 Nondisjunction- failure of homologous chromosomes to separate during anaphase of
meiosis
 Trisomy- condition of having an extra chromosome (Down Syndrome)
DNA technology can change the genetic makeup of an
organism.
Recombination-moving
genes from one
organism to another
(crosspollination/Hybrids)
Genetic Engineeringusing organisms for
beneficial purposes
(insulin production,
fighting viruses)
Complete the practice
questions in your
journal.