Where new gene combinations come from
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
A gamete gets 1 chromosome from each pair. No crossing over happens. Ari deals the chromosome cards of a parent cell. Pair 1 carries genes A and B, and pair 2 carries gene C. With no crossing over, which gamete could not be made?
- a b C, since a light pair 1 chromosome cannot go with the dark pair 2 chromosome
- A b C, since A and b sit on different chromosomes of pair 1
- A B c, since a dark pair 1 chromosome cannot go with the light pair 2 chromosome
- a b c, since a gamete cannot get three light alleles
Chromosome cards (model, not to scale). Crossing over between D and E happens in some cells but not in others. Bo deals a parent cell with D and E on pair 1 and F on pair 2. Crossing over between D and E happens in some cells. How many gamete types are possible?
- 4 gamete types
- 8 gamete types
- 6 gamete types
- 16 gamete types
Read this first
Use this
Chromosome cards (model, not to scale). Parent 1 cell has 2 sets of chromosomes and 2 pairs. Pair 1: a dark chromosome with allele K and a light chromosome with allele k. Pair 2: a dark chromosome with allele M and a light chromosome with allele m. Each pair lines up on its own. Grid: the side edge for parent 2 is already dealt: K m, k m. The top edge for parent 1 is ?.
Esme deals pair cards to the edge of a grid. Genes K and M are on different pairs of parent 1. Which choice lists parent 1's gamete types for the top edge?
- K M, K m, k M, k m
- K M, k m
- K M, K m, k m
- K k, M m
Fruit fly test cross card (Morgan, 1912; the total is model data)
item value genes body color and wing length recombination frequency 17 percent offspring in the model total 1,000 Jun reads that Morgan's fruit flies gave a recombination frequency of 17 percent for body color and wing length. About how many of 1,000 test cross offspring are recombinant?
- About 830
- About 500
- About 17
- About 170
Model test cross counts (model data)
group offspring parental types 880 recombinant types 120 total 1,000 Kira counts a model test cross: 880 offspring look like a parent, and 120 show a new combination. What is the recombination frequency?
- 50 percent
- 13.6 percent
- 88 percent
- 12 percent
Recombination frequencies for genes P, Q and R on one chromosome (model data)
gene pair frequency P and Q 4 percent Q and R 9 percent P and R 13 percent Luz reads recombination frequencies for genes P, Q and R on one chromosome. Map distances add up. Which gene lies in the middle?
- No gene can be found, since percentages do not add
- P, since P and Q have the smallest value, 4 percent
- R, since P and R have the largest value, 13 percent
- Q, since 4 + 9 = 13 matches the P to R distance
Notebook on a cell with 8 pairs
line what the notebook says 1 Each pair can face either pole at the middle, in 2 ways 2 The pairs line up independently, so the choices multiply 3 With 8 pairs there are 2 × 8 = 16 line-ups 4 Crossing over adds more variety on top of this Noah's notebook is about a cell with 8 pairs of chromosomes. One line is wrong. Which fix is right?
- Line 2 should say the choices add up, one 2 for each of the 8 pairs
- Line 4 should say crossing over adds new alleles on top of this
- Line 1 should say each pair has 1 way, with the dark chromosomes on one side
- Line 3 should multiply 2 eight times: 2⁸ = 256
Notebook on a pair of chromosomes
line what the notebook says 1 Each chromosome was copied before meiosis, so it has 2 sister chromatids 2 In prophase I, the dark and light chromosomes of a pair lie side by side 3 The 2 sister chromatids of the dark chromosome swap pieces with each other 4 The swap happens in prophase I, before the pairs line up at the middle Pia's notebook is about a swap of pieces in a pair. One line is wrong. Which fix is right?
- Line 3 should say a dark chromatid swaps pieces with a light chromatid
- Line 4 should say the swap happens in prophase II, after the cells divide
- Line 1 should say the copying happens after the pairs line up at the middle
- Line 2 should say the dark and light chromosomes are identical copies
Claim card (model)
group how offspring are made X budding, so offspring are copies of the parent Y meiosis and fertilization natural selection acts on variation already in the population Tala compares two groups. Group X makes offspring by budding, which gives copies. Group Y uses meiosis and fertilization. Which claim about variation for natural selection is right?
- Group Y offers more, since crossing over happens in both meiosis I and meiosis II
- Group Y offers more, since crossing over makes new alleles that neither parent had
- Group Y offers more, since crossing over, assortment and fertilization make new allele combinations
- The groups offer equal variation, since mutation is the source of variation in each group
Zee claims that if a crossover happens between two linked genes in every meiosis, all offspring of a test cross show new combinations. Which reply is right?
- False, since 25 percent is the most that crossing over can give for two genes
- True, since sister chromatids swap too, so the 4 chromatids change
- False, since crossing over cannot happen between genes on the same chromosome
- False, since a crossover changes 2 of the 4 chromatids, so about 50 percent of offspring are recombinant