Unit 4 Study Guide (Bio)

Unit 4 – Study Guide

I. DNA/Genetic Material

a.       Role of DNA- contains the instructions needed for an organism’s survival.

• $basic unit: Nucleotide$
• $four bases- adenine, thymine, guanine, and cytosine (apple in the tree, car in the garage)$
• $function: store information, copy information from parent cell, transmit information to daughter cells$

b.       Structure of DNA-twisted double helix laddere

• $a. The Phosphate$
• $b. The Deoxyribose Sugar$
• $c. The Base$

c.       What does DNA stand for?

• $Deoxyribonucleic Acid$

d.       What are chromosomes?

• $A structure that consists of a DNA molecule tightly wrapped around packaged proteins$
• $Throughout most of a cell’s life cycle, the DNA is unraveled. The DNA only condenses into chromosomes during cell division.$

e.       What are homologous chromosomes?

• $a pair of chromosomes that are similar in length as well as gene and centromere position$

f.        Define haploid and diploid.

• $Haploid- a full set of chromosomes$
• $Diploid- a half set of chromosomes.$

g.       What is the normal human chromosome number?

• $46 chromosomes$

h.       What are gametes?

• $a mature, haploid reproductive cell that is created as a result of meiosis$

II. Meiosis

a.       When does crossing over take place?

• $Crossing over takes place during synapsis. Creates genetic variation and why your siblings are not identical to you.$

b.       What is the main purpose of Meiosis?

• $To produce an offspring that is half of each of the parent’s chromosome, rather than being identical to one of the parents.$

c.       What is the result of Meiosis?

• $Four genetically different cells$

III. Mitosis

a. What is the results of Mitosis?

• $Two genetically identical cells$

IV. Inheritance Terminology

a.       Gene

• $determines an individuals traits, genotype$

b.       Allele

• $one of two or more DNA sequences occuring at a particular gene location$

c.       Trait

• $specific characteristics of an individual, phenotype$

d.       Homozygous

• $BB or bb, two of the same alleles and can be either dominant or recessive$

e.       Heterozygous

• $Bb, one of each allele$

f.        Dominant

• $BB, the one that is expressed$

g.       Recessive

• $expressed when the genotype is homozygous, bb$

VI. Punnett Squares (reference practice sheets)

a.       Single Trait

• $normal punnett square$

b.       Codominance

• $both genes are equally strong and visible$

c.       Incomplete Dominance

• $results from a cross where both parental contributions are visible, creating a genetically unique phenotype$

d.       Sex-linked

• $the gene is found on the X chromosome (x^n), occurs more often in men (XY) with the possibilities being XrY or XRY and women being X^RX^R, X^RX^r, or a carrier of X^rX^r$

V. Pedigrees

a.       Rules for Autosomal vs. X-linked

• $If most of the males in the pedigree are affected the disorder is X-Linked$
• $If it is a 50/50 ratio between men and women, the disorder is autosomal$

b.       Rules for Dominant vs. Recessive

• $If the disorder is dominant, one of the parents must have the disorder$
• $If the disorder is recessive, neither parent must have the disorder because they can be heterozygous$

c.       Know all symbols and how to differentiate between a marriage and offspring

d.       Know how many generations are listed

• $each vertical line (see above)$

e.       Know the difference between Male and Female

• $female- circle$
• $male- square$

VII. Karyotype Interpretation

a.       Know how to tell if it’s Male or Female

• $female xx male xy$

b.       Know whether the Karyotype is demonstrating a disorder or not

• $extra chromosomes, etc$

c.       How are karyotypes arranged?

• $ordered from biggest/longest to shortest/smallest and the XX or XY genes$

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