Download GENETICS – Chapters 11, 14, 15 I. MEIOSIS: (11

GENETICS – Chapters 11, 14, 15
I. MEIOSIS: (11-4)
a cell division process that reduces the number of chromosomes in cell by half, this creates the gametes (sex
cells). Sex cells are sperm cells for ____________________, and egg (ovules) for ____________________.
Humans have 46 chromosomes in most of their body cells, except their gametes which have __________
chromosomes. The process of making haploid cells is initially the same as mitosis; however, through a
second division the chromosomes are further separated.
Draw and label the steps of Meiosis pages 324-325:
Meiosis I:
Meiosis II
II. GENTICS:
Chapter 11-1
A. Genral info:
1. Genetics is the branch of biology that deals with the study of heredity. Heredity is the
passing of traits from parents to offspring. Traits are the physical features in the offspring.
2. Mendel Gregor who was an Austrian Monk and considered the “father” of genetics, was
one of the first to show, record and predict how traits are passed from parents to offspring. He
published his findings in 1865; however, they were not accepted until the 1900’s. He studied
pea plants recognizing that the unique characteristics they had were easy to chart and record.
He identified various traits as dominant alleles
(_________________________________________________________________________
_____________________________________________________________________) and
recessive alleles (____________________________________________________________
________________________________________________________________________).
Mendel called the Parent organisms (P) and called the offspring Filius / filia (F1=first
generation, F2= second generation) excetra.
He developed two conclusions (310):
1.
2.
Mendel crossed F1 generations and discovered the F2 offspring showed approximately _____
recessive traits. Mendel began to show the Law of segregation in genetics, which states: 312
________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
B. Probability:
3. One Gene: Probability and possibilities are calculated in various ways.
The principal of probability is used to predict the outcomes of genetic crosses. Punnett
squares are used to show possible gene combination.
The possible gene combinations are called the ______________________. The physical
traits developed are called the ________________________.
These two are not always the same. We are dealing with a single set of Genes
A. Dominant traits: stronger of the traits, often represented by a capital letter.
Ex.: in pea plants tall (T) is dominant therefore any plant that has a gene for a tall
plant will be tall. Since genes occur in pairs if the plant has TT it is called a pure tall
plant or homozygous plant.
B. Recessive traits: weaker of the traits, does not show up unless there are two (2)
recessive genes.
Ex. a short plant would be tt.
*When dealing with incomplete(_________________________________) or co-dominant
( _____________________________________________) traits you use two separate
capital letters for each trait. Red =______, White =_____. These are also called purebreeds or ________________________________________ organisms.
C. Hybrids: a trait that has two (2) or more different genes. If dealing with a
dominant and recessive trait, the offspring will express the dominant trait even
though it has a gene for both. The genes would be written as (Tt), this plant would be
tall. These organisms are considered to be heterozygous.
Genotype:
Phenotype:
**When dealing with an incomplete dominant trait, the trait would blend and you would use
two different capital letters to represent each of the traits. Ex.: a pink flower (RW); R = red,
W = white, when these two genes combine for an incomplete dominant trait they blend
together. Since gene occur in pairs RR=red, WW=white
Genotype:
Phenotype:
*When dealing with codominant traits, you would also use two different capital letters to
represent the genes. However, instead of blending together both traits show up. Ex.: a roan
cow has white (W) and red (R) fur, each fiber of fur will be either red or white not pink.
4. Dihybred crosses: crossing two or more sets of Genes
Dominant & recessive crosses: pure tall green (TTGG) X pure short yellow (ttgg)
Genotype: ______________________________________________________________________________
______________________________________________________________________________
Phenotype: _____________________________________________________________________________
_______________________________________________________________________________
3. Genes (alleles): are locations on chromosomes that determine hereditary traits. All
organisms have at least two or more genes which make up traits. These genes are on paired
chromosomes that match up at fertilization (joining together of egg and sperm). Genes are
made up of DNA (deoxyribonucleic acid), and RNA (ribonucleic acid).
DNA: is comprised of four nitrogen based substances; Thymine (T), Adenine (A),
Guanine(G), and Cytosine (C). They pair up as shown A = T, and G = C. DNA occurs in a
structure called a double helix, looks like a twisted ladder. When DNA copies itself it is
called REPLICATION.
RNA: is comprised of four nitrogen based substances; Uracil (U), Adenine (A), Guanine (G),
and Cytosine (C). U = A, G = C.